Thankyou for you replies!
I never really associated gratitude with mudita before, but now that I think about it they are closely related, and I never thought of directing mudita towards oneself, which sounds like a good idea. The way I was thinking of gratitude was more along the lines of reflecting on the four requisites and gratitude towards ones parents, but I'm wondering, would being grateful for someone elses' fortune be a highly developed form of mudita? I always saw sympathetic joy as rejoicing in others successes, but being grateful for others successes seems like it would be quite a lofty aspiration, or perhaps I'm taking it to extremes beyond what the Buddha taught? I'm interested to know.
"The heart of the path is quite easy. There’s no need to explain anything at length. Let go of love and hate and let things be. That’s all that I do in my own practice." - Ajahn Chah