Not too much, not too little. Somewhere in the middle. I think this is related to some concept in Buddhism. Alternatively, it can be due to human psychology where it gets fed up of artifical scarcity, and also gets fed up of lack of change (which is where "too much" come from, like "too much school")
I don’t follow anything to the full. Otherwise, the flaws of each philosophy will clearly show. In fact, there are many things that this rule applies to. Most thoughts, when taken to the extreme, become absurdity; one famous example is PURE Nihilism (suicidality?). Another one is Altruism: If Elon Musk donates $100 to everyone in the world, he would instantly go bankrupt. And it can also be that human brains actually function better when things change due to lowering boredom, like job rotation. That’s Neural Habituation. Return on investment actually drops when doing one thing for long periods of time, like that one time when I did multiple math past papers in a row, I felt like a zombie afterwards and didn’t perform to good ability.