"And the Lord said, Simon, Simon, behold, Satan hath desired to have you, that he may sift you as wheat: But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren." Luke 22:31-32 (KJV)
Are you in need of a conversion? You might be thinking, "No. I'm already a Christian. I already believe." First, we must uncouple the thought that if one believes (in God, Jesus and their relationship to each other and us) that it makes you a Christian. "You believe that God is one. You do well; the demons also believe, and shudder," James 2:19. Are demons Christian? Of course not.
Secondly, let us consider the case of Simon (Peter), considered by some to be the foremost apostle. Though he was often the "go to" guy, one who was part of Jesus' inner circle, who had faith enough to walk on water and issued the God inspired confession that Jesus is in fact the son of God (Matthew 16:16-17), he was also one who denied Christ three times when the Lord, arguably, needed him most. The context of the Scripture indicates that Satan had requested permission to attack him and weaken his faith. This may seem odd, but one only need think back to Job to see that this was not a unique occurrence.
Beloved, we are all at different places in our spiritual walk. We likewise are all under a constant barrage of temptation both from Satan and our own lusts (James 1:14). This can have the effect of us failing in our faith. That can manifest itself in many different ways in many different people. It may cause us to "play church," wearing a mask of piety to cover a life of sin induced inner conflict and despair. Some are married to their positions, responsibilities or reputation in the congregation and community and hang on to them even though their hearts may not be right. Some fall out of fellowship altogether due to their inner struggles.
Whatever the effect may be, rest assured that Jesus knows and understands our trials (Hebrews 4:15) and prays that we will be delivered from them, or more to the point, that we will be converted. This is not to say that we are not Christians or never were, but that he is praying for a return to righteousness and triumph over trials. And he prays this not just for our own sake, but for the sake of those who we can help who may go through similar seasons.
Challenges to our faith will surely come. Let us do all we can to remain steadfast and never have a reason to return to that which we should never have departed. "Submit therefore to God. Resist the devil and he will flee from you," James 4:7