For most of my highschool years I was enrolled in College Prep classes. This was to prepare me for college, to give me a head start, to make my college days more successful. In a sense our childhood is adult prep. Our parents, teachers, pastors and others are preparing us for life beyond childhood. We need to be ready for life so we are tested, stretched, admonished, helped and challenged so that we will be ready.
It is interesting to look at faith through the eyes of James, the half brother of Jesus and author of James. He sees trials as a means of letting patience work on our faith; temptations endured a means of crowning our faith and works as a means of perfecting our faith. Our works are a part of our salvation in the sense that they prove that we are saved and they are part of the perfecting or sanctifying of our faith.
In James 2:26 we read: For as the body without the spirit is dead, so faith without works is dead also. (James 2:26 NKJV) Works are the fruit of faith and we see this displayed in the lives of believers from the beginning. Faith spawned works. The testing, stretching, admonishing, and challenging are all a part of our eternity prep, the testing of our faith to bring us to the crown of life. We can't earn our salvation, that has been paid for by Jesus; but, we can and must let trials and temptations, prove us, perfect us, and prepare us.