Does anyone else struggle with performance and mastery?

This may not be a topic suitable to HN, but maybe it could spark some interesting discussion.

I'm almost in my mid 30s now and I've been a gamer/game-player for probably most of my life. I've noticed at least in the last few years that developing mastery at various games or even just performing well and consistently has become quite a lot more challenging than it was say in my early 20s. I can't say I've ever been in the top 0.1% of anything I've tried, but I have come fairly close in some things after years of effort. In my case, it seems there is a wall where it starts becoming difficult for me (which it seems like that wall is different for everyone based on any number of things), and my motivation quickly starts dropping off. Either that, or I get so frustrated trying to work through it that it ruins my days and then I get less motivated again. I would imagine there is a different breaking point for everyone depending on a number of things, like aptitude, attitude, and motivating factors toward improvement.

I originally thought it was just mostly related to how sharp you are as a person. It seems like that can help, but it isn't the most important factor at all. I know HealthyGamer.GG did some discussion about this kind of thing, and he talked about the strongest factor in research being that of "cognitive flexibility." Is this something that is trainable? Is this something where the crystallization of intelligence that occurs as we age acts as a hindrance? What kinds of strategies to more competent HNers use to combat this?

Do others on HN struggle with mastery as they get older? I'm sure many of you have children now and because of such probably have far less time to dedicate to these kinds of things. I have a lot of free time on my hands nowadays, so all I'm really doing is just trying to get better at things. So measuring short of where I want to be feels a lot more painful.

Something else I find weird about it is that some of these activities I'm actually quite motivated to do, so clearly being more skillful at them is a strong net positive both in the short and long-term. They aren't all games. Knowing that and putting work in but not getting close to where you want to be even with significant effort is troubling.

Is it as simple as the Ronnie Coleman quote but applied to every domain? "Everybody wanna be a body builder but no one wants to lift these heavy-ass weights" Ronnie Coleman.

I imagine my health issues and life circumstances probably act as a hindrance for focusing and maybe even the whole process, but I don't think it is healthy to place blame on those things, especially when I'm not really able to control them fully.

I mentioned games at the top, but I'd like those reading to think about this with anything they are trying to master--programming, writing, musical instruments, languages, anything like that.

Thanks for reading.