One of the wisest men to ever live on the planet said that the joy we feel isn't because of circumstances in our lives, but rather, where our focus lies.
I find that when I step outside of myself, out of my own little box of pity parties, self-justifications, rationalizations and explanations as to why I should be feeling horrible, and instead focus on someone else and how they might be feeling, I find that I can feel joy and gratitude more readily.
Why is that? I feel that as a Christian woman, I have been taught to rely on Jesus Christ and his gift of the Atonement. It is a real and working entity that has such power, if I let it. He has given us teachings and examples in His life that are so powerful. If I truly follow those examples and teachings, I can access the power that He was teaching those who had eyes to see and ears to hear.