James writes,

Blessed is the man who remains steadfast under trial, for when he has stood the test he will receive the crown of life, which God has promised to those who love him. Let no one say when he is tempted, “I am being tempted by God,” for God cannot be tempted with evil, and he himself tempts no one. But each person is tempted when he is lured and enticed by his own desire. Then desire when it has conceived gives birth to sin, and sin when it is fully grown brings forth death.

James cannot possibly be writing about sin in general. He is talking about the way people in the Church make shipwreck of the faith. Rather than growing by faith through trials into wisdom, they allow desires to grow into sins and then keep growing rather than repenting. The point is twofold: 1. sin is dangerous and will lead you to destruction and 2) you have time to repent and return so make use of that time to cut it short.

Of course, a person who has left his desires unchecked, so that they give birth to sin, might not be in the best mindset to turn from that path. Christians need help from their fellow Christians. So James ends his letter with an exhortation that hearkens back to what he wrote near the beginning of his letter:

My brothers, if anyone among you wanders from the truth and someone brings him back, let him know that whoever brings back a sinner from his wandering will save his soul from death and will cover a multitude of sins.