One of the best skills I picked up from my pre-comics life working in offices was the ability to power nap. I have insomnia, so I'm often working from a deficit. When I'd get my 15-minute breaks, I'd go down to my car, put the seat back, play some music through my headphones, and sleep for about 2 songs. I even remember dreaming, so it was some decent quality sleep. Then, I'd go back up to the office feeling refreshed.
These days, I only do this in extreme situations, but sometimes I'll "shut down" instead. I don't really sleep, but I close my eyes and try to tune out everything around me for about a minute. It's more of an introvert recharging moment than anything, but it can REALLY help me.
Rock on, guys, and never stop drawing.