A friend of mine once asked me why James in his letter says to call the elders to pray for us when it is heard in my teachings at TRGN that every Christian filled with the Holy Spirit has everything he needs to have his prayers answered.
I thought I'd let you benefit from my answer....

If we go back to the beginning of his letter, we understand that James is talking to Christians with a Jewish background, who are being persecuted outside of Israel. But he also speaks to a group of Christians (not necessarily from the same local church) who do not agree with each other and hurt each other.
James begins the first 4 verses of his letter by explaining that he writes for born-again Jews who are outside of Israel and who, in addition, are persecuted.

1  James, a bondservant of God and of the Lord Jesus Christ, to the twelve tribes which are scattered abroad: Greetings.

2  My brethren, count it all joy when you fall into various trials,

3  knowing that the testing of your faith produces patience.

4  But let patience have its perfect work, that you may be perfect and complete, lacking nothing.

These people are therefore in great distress, overwhelmed by persecutions ; some of them even lost their lives according to Act 8:1 (account that is at the same period of time).
There, James exhorted them so that they could regain a mental strength that would encourage them to continue the fight of the Christian life. It seems that they may be persecuted by non-born again people and more wealthy than they are... Perhaps in the field of business, because the Jews who had made the decision to leave Jerusalem had often done so to do business elsewhere. 

9  Let the lowly brother glory in his exaltation,

10  but the rich in his humiliation, because as a flower of the field he will pass away.

Here again, we see that there is no question about suffering in the physical sense.
But James urges them to use what God has given them to get out of this situation.

21  Therefore lay aside all filthiness and overflow of wickedness, and receive with meekness the implanted word, which is able to save your souls.

It must be understood that James' context is about born-again Jews, who were to suffer dishonest behaviours in the professional and personal fields. And some of them were tempted to do like the others in front of them, and to return evil for evil.

12  Blessed is the man who endures temptation; for when he has been approved, he will receive the crown of life which the Lord has promised to those who love Him.

13  Let no one say when he is tempted, "I am tempted by God"; for God cannot be tempted by evil, nor does He Himself tempt anyone.

When we look more closely, it's not very complicated, we only have to read Jacques' letter and at the same time look and imagine the whole scene I just described.
Then when James talks about putting the word into practice, he means: "Put into practice what you hear in the teachings, integrate them into your daily lives, and you will see that things will get better".

22  But be doers of the word, and not hearers only, deceiving yourselves.

23  For if anyone is a hearer of the word and not a doer, he is like a man observing his natural face in a mirror;

He also says not to get into quarrels with these people:

26  If anyone among you thinks he is religious, and does not bridle his tongue but deceives his own heart, this one's religion is useless.

In chapter 2, James explains not to return evil for evil, and just because these people persecute them it does not mean they should act like them, in a bad way. 

8  If you really fulfill the royal law according to the Scripture, "You shall love your neighbor as yourself," you do well;

9  but if you show partiality, you commit sin, and are convicted by the law as transgressors.

There are many more verses in this sense, but here are just a few examples.
It is also possible that some Christians who were murdered may have provoked revenge from other brothers who wanted to do their own justice.

11  For He who said, "Do not commit adultery," also said, "Do not murder." Now if you do not commit adultery, but you do murder, you have become a transgressor of the law.

12  So speak and so do as those who will be judged by the law of liberty.

13  For judgment is without mercy to the one who has shown no mercy. Mercy triumphs over judgment.

  Chapter 4 reveals the conflicts  between Christians.

1  Where do wars and fights come from among you? Do they not come from your desires for pleasure that war in your members?

2  You lust and do not have. You murder and covet and cannot obtain. You fight and war. Yet you do not have because you do not ask.

3  You ask and do not receive, because you ask amiss, that you may spend it on your pleasures.

11  Do not speak evil of one another, brethren. He who speaks evil of a brother and judges his brother, speaks evil of the law and judges the law. But if you judge the law, you are not a doer of the law but a judge.

Another example shows that many of the persecutions and quarrels between these people also came from an activity mainly oriented towards (professional) trade.

13  Come now, you who say, "Today or tomorrow we will go to such and such a city, spend a year there, buy and sell, and make a profit";

Then James speaks in chapter 5 verse 10 about taking an example from the prophets who suffered in patience.
Then from Job in verse 11.
And we get to the subject we're interested in.
In Chapter 5

13  Is anyone among you suffering? Let him pray. Is anyone cheerful? Let him sing psalms.

The word suffering here refers in the original to moral suffering in the sense of affliction, moral weakness. 
Verse 14: James speaks of the sick people from a moral point of view, such as depression, for example, which is above all moral.
In other words, he said to them: "In this case call the elders, because in your condition you need strong brothers to help you, because your mental condition is not strong enough to cope on your own. You will not be able to activate the necessary faith in you so that your prayers will be successful.
Here are verses from the New Testament that speak of "sick" in the moral and not physical sense, it is the same original word as in James 5: 14

Acts 20:35 I have shown you in every way, by laboring like this, that you must support the weak. And remember the words of the Lord Jesus, that He said, 'It is more blessed to give than to receive.' "

Romans 4:19 And not being weak in faith, he did not consider his own body, already dead (since he was about a hundred years old), and the deadness of Sarah's womb.

Romans 8:3 For what the law could not do in that it was weak through the flesh, God did by sending His own Son in the likeness of sinful flesh, on account of sin: He condemned sin in the flesh,

Romans 14:1 Receive one who is weak in the faith, but not to disputes over doubtful things.

Romans 14:2  For one believes he may eat all things, but he who is weak eats only vegetables.

1 Corinthians 8:11  And because of your knowledge shall the weak brother perish, for whom Christ died?

1 Corinthians 8:12  But when you thus sin against the brethren, and wound their weak conscience, you sin against Christ.

2 Corinthians 11:21 To our shame, I say that we were too weak for that! But in whatever anyone is bold--I speak foolishly--I am bold also.

2 Corinthians 11:29 Who is weak, and I am not weak? Who is made to stumble, and I do not burn with indignation?

2 Corinthians 12:10  Therefore I take pleasure in infirmities, in reproaches, in needs, in persecutions, in distresses, for Christ's sake. For when I am weak, then I am strong.

2 Corinthians 13:3  since you seek a proof of Christ speaking in me, who is not weak toward you, but mighty in you.

2 Corinthians 13:4 For though He was crucified in weakness, yet He lives by the power of God. For we also are weak in Him, but we shall live with Him by the power of God toward you.

2 Corinthians 13:9 For we are glad when we are weak and you are strong. And this also we pray, that you may be made complete.

It is true that there were two sources of discouragement that led some of these Christians to fall into discouragement, then into weakness, then into sin.

1/ The external percussion of everyday life (linked to their professional and personal life)
2/ persecution because they were Christians (linked to their belief).

Acts 8:1  Now Saul was consenting to his death. At that time a great persecution arose against the church which was at Jerusalem; and they were all scattered throughout the regions of Judea and Samaria, except the apostles.

Acts 9:1-2  Then Saul, still breathing threats and murder against the disciples of the Lord, went to the high priest  and asked letters from him to the synagogues of Damascus, so that if he found any who were of the Way, whether men or women, he might bring them bound to Jerusalem. About 37 years after Jesus Christ.  

James' letter was written about 45 years after Jesus Christ. I think it can be considered that the persecution could have lasted at least 8 years. And if James was urged to write them a teaching letter, it is because things were not just at their beginning.
For the record, Paul had already been converted at that time for at least 6 years.
Of course the dates in the chronological Bible are not perfect, but I think they nevertheless give us valuable indications on which we can base ourselves with a +/- range, to study.

It would therefore strongly appear that the great persecution of Christian Jews outside Israel coincided with the same period as James' letter.
Even if we consider that this is not the case, we can still conclude that these "sick" people of whom James speaks are Christians so weakened that they can no longer pray effectively for themselves.  And so in this case, and in this case only, James advises them to call other Christians who are morally stronger, who can pray for them. But this is not a rule that should be applied every time we need to pray, because that is not at all what James says in his letter. Far too many Christians systematically call upon elders or other brothers and sisters when they need to pray. Over time it becomes a habit, and it keeps them in a constant state of weakness. These same people are never able to manage themselves on their own, satan keeps them in thoughts like: "You don't have enough faith, call quickly someone because you are not strong enough, your prayer will never be as powerful as that of others". So we come to make it a rule to call other people to pray for us when a problem arises. Prayer with others is no more powerful than alone, for we have all received the same power that raised Jesus Christ from death in our spirit.

When a born again person has no problem with praying, concentrating and using his authority, then his own prayer will be just as powerful as any other, as long as he activates the faith that is already in him, knowing that all Christians have received the same measure of faith. Of course, there is no question of leaving our brothers and sisters in need, but over assistance is not what God recommend. Too many Christians take advantage of this assistance that others over offers, asking: "Who wants to be prayed for? ».
Let us understand once again that it is not a bad thing to help when there is a need. But autonomy or self-sufficiency is very important, it involves teaching. Those who ask for prayers when they have everything they need to do it themselves must change that. In the same way, those who offer excessive prayers without worrying about whether the person is able to do it himself or not, must also change that. The key is to teach Christians who need it to pray successfully, not to over assist them. It is autonomy from each other that will make the Church of Christ stronger.

Bye for now.