This sounds counter-intuitive, but sometimes I find it helps to just FINISH something, even if the finished product is really crappy and not what I wanted to do at all. It's the finishing that matters. One you finish one thing, it is easier to finish the next thing.

I like what Michanne described with her BFA project - sometimes we have to do something that doesn't seem good or useful in order to get to the end result we're looking for.