It never ceases to amaze me how effective taking longer breaks is. Not just for programming, but also for drawing.
Stuck on some complex code? Do something else, get back to it a few months later and suddenly it's clear what's lacking and how to make it better.
Did some shading on a head, but it's only okay-ish and you don't know what to do? Draw other things, try shading heads again months later and suddenly it just works out.
It happens all the freaking time to me. It's magic.