Taking the pressure off always helps, but I’m reading a book at the moment that explains how brain wave frequencies work and what you said about taking a nap rings true.

Basically, if you’re in a relaxed, pre-sleep state, your brain waves will enter theta frequency, which (along with the relaxed-but-not-dozing stage before that, alpha frequency) is optimal for creativity.

If we’re too stressed or highly strung, our brain waves will work at beta frequency, which is great for giving presentations and stuff but not creativity.

Apparently, we can coax our brain waves into alpha/theta frequency by listening to baroque music, or Enya!

Anyway that’s just from one book and I’m no expert (sorry for the long comment!). It does seem relatable though, I’ve experienced similar when in a dozy state.