Sometimes, it helps to step away from something for a while.

I work in software, and there are often times when I'm stuck trying to figure out why something's not working. I'd keep persisting into the wee hours of the night, but I just can't figure it out. Partly because I'm exhausted.

But then I get some rest, or take a walk outside in the fresh air, or get a warm, relaxing shower, then all of a sudden, a solution might come to mind.