I experience writer's block when I'm working on a long project like a novel. Things start to feel monotonous, my head isn't in it. Something like that is happening. So when it starts feeling like a chore instead of something that I really want to do, I break it up into smaller pieces.
I have a few methods of doing that. The first is to write the parts that I'm excited about instead of the ones that I'm trudging through. Another is to treat the long story like a short story and then elaborate on it.
Block happens. Whether its because you're challenging yourself or you're not challenging yourself enough. But a good solution to any large problem is to break it up into smaller pieces. Jack White has a whole song about it.