Because of a profound yet simple truth found in James. Yes. You read right, James, not a Pauline epistle.
Consider it all joy, my brethren, when you encounter various trials, knowing that the testing of your faith produces endurance, and let endurance have its perfect result so that you may be perfect and complete lacking in nothing. But if you lack wisdom let him ask of God, who gives generously and without reproach, and it will be given to him.
When you encounter various trials...[various is nicely explained here]
to have joy... but why should we have joy? What is this joy rooted in? The joy is knowing that the temporary pain and trials that come.. are to grow us, grow us in endurance. So that we might be more and more like Christ. Complete.
so rejoice knowing that it produces endurance. and through each trial, each test. the endurance brings us closer to our Savior.
more on the subject here
