I was talking with one of my "mentors", and I was talking about my week and he said, "Where are you finding your joy?"
Yikes! I had never thought in those terms before. I know what makes me happy and what makes me sad...but I never thought about those things being where I derive my joy. Joy that comes from the Lord is unwavering, because he is unwavering. If we find our joy in the Father who loves us, will never forsake us, created us fearfully and wonderfully, and has a zest for our lives that goes above and beyond our own, then we will be constantly joyful. Finding our joy in earthly things will lead to disappointment, frustration, and discontentment. Can you name even ONE earthly pleasure that is constant and never changes or becomes less pleasurable? I can't.
My friend posted a series on Biblical Joy on his blog and it's been really helpful to me (over and over and over and over and over). I definitely recommend it!
Paul is my favorite Biblical figure, mostly because he is joyful in situations where I know I would be a whiner. In Philippians 4, he says (while chained to a Roman guard):
Rejoice in the Lord always; again I will say, Rejoice. Let your reasonableness be known to everyone. The Lord is at hand; do not be anxious about anything, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus. (ESV)
If Paul can find joy in this situation (that is far worse than anything I've had to face), I think it's plausible to be able to do the same thing. 1st Thessalonians 5:16-18 tells us, "Be joyful always, pray continually, give thanks in all circumstances." (ESV)
I pray for the discernment to know when my joy is coming from somewhere else, and for the wisdom to find my joy in the one who will never falter in his promises.