I've discovered that my brain works better when I jump into VR right around sunset. I can't handle the idea of the sun going down at 5pm. It puts me in this weird timeless state where I think "It can't be dark before six! Is it midnight? Nine? Four in the morning? Who knows???" So I take off to an alien planet, or a forest, or a beach instead and have light shining directly into my eyes, and it seems to work.
I noticed something similar when driving on long trips. If I take a break to go inside a restaurant around sunset, then I feel refreshed and ready to go again.