James 1:2-4 NIV
Consider it pure joy, my brothers, whenever you face trials of many kinds, because you know that the testing of your faith develops perseverance. Perseverance must finish its work so that you may be mature and complete, not lacking anything.

They are 2 things which we as Christians need to have to come through trials and temptations;

1.  Faith;  to be believe that at the end of our troubles we will be stronger spiritually than we were before it began;.  Faith to believe that God is with us every step of the way through our trouble and that He never gives up on us.

2.  Patience;  to walk the rough road that lies ahead of us regardless of what it may bring; we also need the patience to wait for God to direct us and lead us out of rough road.

When things start to get to us (and this could be anything from our children, our spouse, or jobs, just everyday stuff) we can not only put up with them but can have victory over them if we have faith and patience.

In the 2nd verse we read that we should try to be joyful when trials come. 
Why?
When we finally come through the trial / temptation, whatever it may be, if we are clinging to Him with faith and are waiting on Him to direct us with all the patience that we have, we grow spiritually !!

Spiritual growth is an essential part of a Christians life.  When we grow spiritually we are growing more like Jesus in character and personality, to the Glory of God, and that means that we are working harder than ever to do His will.

So when trials and temptations come don't be discouraged.  Just do God's Will and grow, and be joyful because He is giving us a chance to grow.  Don't be sad and gloomy because you are in a trial.  Let the world see you smile and they will see Jesus in that smile and they will know He is real and that He is always there for us to help us and guide us. Praise God !!

However, we are real people, with real emotions, and He understand that.  he understands we have down periods, and depressions, and anxieties.  The important thing is that in the midst of these human emotions, we look for Him, and wait for Him to lift us up and rescue us.

In the 4th verse He is telling us that if we are patient,  doing His will, trying to live right, that He makes us complete, lacking for nothing.

What a Mighty and Wonderful Saviour that we serve !!