Speaking of "pure joy," sweet tea is one of my favorite delicacies.  You have probably noticed that when you add sugar to tea, the sugar settles to the bottom.  The only way to make the tea sweet is to stir it.  It is the stirring that causes the sugar to permeate the entire pitcher of tea.

You are the pitcher of tea, and your faith is the sugar.  That faith is in you, but it doesn't really transform you until there is some stirring.  That stirring is what James refers to as "trials of many kinds."  God uses the trials you experience to change you and make you stronger.  When your life gets stirred up, God uses it to build your perseverance.  In fact, it is impossible to develop perseverance without that kind of stirring.  The only way to develop a "never give up" attitude is to survive something that tempts you to give up.  God is so good that even your trials can be reason to rejoice, because those trials strengthen your perseverance.