Count it all joy, my brothers, when you meet trials of various kinds, for you know that the testing of your faith produces steadfastness.  And let steadfastness have its full effect, that you may be perfect and complete, lacking in nothing.
(James 1:2-4, ESV)

Notice that there is a purpose in our trials.  Our trials are a testing of our faith.  Not to see if we have faith, but to test our very real faith.  The word has the idea of refining or purifying.  You put metal in a fire to melt it down and drain off impurities.  In the same way, our times in the fire are designed by God to refine and purify our faith. 

And this testing produces steadfastness or endurance.  You are more able to endure the same trial today than before because it has developed in you this steadfastness.  It is like lifting weights – you can endure more repetitions and more weight as your muscles are developed.  And you can endure more trials and harder trials as your faith is developed and strengthened.  You are gaining the ability to faithfully endure, to remain steadfast.

And this steadfastness then must have its full effect.  It must keep developing so that you might be perfect or mature – mature in this life, and perfect in the life to come.  So that one day you will be complete, lacking in nothing.

Your trials exist to help you grow in your faith and steadfastness to make you mature in Christ.  There is a purpose in your trials.

So rejoice expectantly.  Rejoice when you have trials because you know that it brings maturity.  We rejoice not in the trial but in the purpose.  We rejoice in expectation that our suffering is for our ultimate good.  Which means that we might at same time be weeping, struggling, crying out to God, and lamenting before Him.  We are not denying the hardship and all sorrow and struggle of our trials, we are just remembering the purpose.  So even as we wrestle, we can rejoice expectantly.