Comment by xnx

It may sound a little woo woo, but I definitely feels this. After duration of difficult mental work (often difficult reading) I can feel my ability to focus slipping and eyes getting heavy. If I can successfully take a short deep nap (sometimes less than 15 minutes) all that is flushed away and I can focus again. Weird analogy, but a the relief is similar to emptying a full bladder. Related, not napping in these circumstances seems like it would be very unhealthy and damaging.