Another good reason for taking breaks: I know a lot of musicians who "level up" by taking breaks. Stop playing entirely for a couple 2-3 days and then come back to it. I'm not really sure how it works, but it's happened to me countless times.

I experience this too, and not just with music but also with other skills. I plateau on something, get frustrated, stop it feeling guilty, then come back to it next week (or even longer) expecting I got rusty for lack of practice, and not only I did not get rusty but I actually got better.

I call it the "offline progression". Obviously you can't get better by not simply doing things so it only happens in specific circumstances, and I don't know when. I think it has to do with overdoing; maybe it's not so much that resting improves your skill, but that the skill is already improved but you can't see it because you've exhausted your mental resources, and taking a break lets you actually access those new synaptic pathways. (I recall WoW originally had an "exhaustion debuff", and players hated the feeling of being punished for playing, so instead they called the debuffed state "normal" and gave a "rested XP buff" for taking a break; functionally the same thing but now it feels like getting a treat.)