www.bible.com/111/jas.5.13.niv
James is not telling you to only pray when you’re in trouble. However, he is telling you that your first reaction to problems, difficulties or troubles should be to be pray. Must of us when we run into problems will try and solve them on our own. This doesn’t help and not only doesn’t it help but it only makes the problem worse. If you’re in trouble, facing a problem or going through a difficult time remember to take your troubles, problems or difficulties to God first.
In the second half of this verse James is again not telling you to just praise God in the good times. This half of the verse is a reminder that God is the source of all things that you should always have attitude of praise. You may not feel happy now, but if you think back and reflect on your life you will find that there things that you can praise God for. As you praise God for these things you will find that will become “happy” or “content” in your circumstances.