I think it helps to do something that I liked to do when I was very young, before any kind of depression set in. It helps me temporarily, at least a little bit, kick back into the mindset associated with it, back when everything was fine.

I also try doing things that take 100% of my concentration and thought power, like math problems. I don't have any brainpower left over to feel things, to feel how I feel about feeling things, etc. because all I have room to think about in my brain is finding x.