Basically the title.

Why the problems seem so much easier if you go to sleep and return to it the next day? It happened to me numerous times. I struggle for hours with a problem, I give up and move on with my day, I return to it in a day or two, usually I don't remember the statement, but after reading it I solve it almost effortlessly. It is like my brain solves the tasks on its own throughout the day, but I find it hard to believe that it is able to do that if I don't even remember the statement. Sometimes I wonder why I bother thinking about a problem at all if I get stuck for more than 10 minutes. I know that almost certainly I will be able to solve it the next day (if I pick an appropriate difficulty for me obviously).

I have pretty much 0 knowledge on how the brain works, and I wonder why this weird thing happens. I know that it is a common knowledge to "sleep on the problem", I was told that in school for example, but I have not seen anyone talking on how MUCH it affects the results.

I also wonder, if it possible to master this "power" lol?
It sounds weird, but I have an "ultimate move" during the contest to go to the toilet, for some unholy reason I consistently was able to find creative ideas in a span of several minutes I spent there. It seams like forgetting about the problem, and then returning to it works just like turning a device off and on, seems to fix most of the problems. But it is so hard to do it during a contest, especially when there is almost no time left. I also know that skipping a problem and then returning to it might be effective when you are stuck, but the effect is so much weaker for me. It helps, but just a bit.