Jet lag means I'm doing nothing but roam around the kitchen munching on random food items, then folding in a heap thinking it's two o'clock in the morning. But knowing I can't be productive frees my mind to roam (and munch on random items of weirdness).
Here, for your delectation and delight, are the fruits of others' intellectual roaming:
We all need down time. It's where the weird and wonderful comes from. Today I'll do nothing in particular. I urge you to do the same.