You might have heard the expression "hard work beats talent when talent isn't working hard." A minimum threshold of talent is a necessary, but not sufficient, condition. I suspect you have met or exceeded that threshold, so effort will drive your results.
Now that I think about it, I feel like the problem is that I don't think I quite meet this threshold. At the same time, I don't have a single overwhelming interest which I would want to pursue; instead I have multiple I'm interested in to varying degrees. Experience has taught me to be cynical and realize that passion is a fleeting thing. My experience suggests that I could have become world class at something if I had found a "calling", but because my efforts were dispersed, and perhaps because I didn't have any teachers who could teach me about the topics I enjoyed and a complete lack of any peers in my areas of interest, it did not happen and I lost interest after a few years, and somehow accepted that I would have to teach myself everything in school because no one could teach me what I wanted to learn. Which again leads me to wonder whether you should just commit to a path and stick it through, even if you don't like it, because it almost feels like a waste to let that potential slip away.
I feel like this idea of wanting to do something well (near world-class) is so entrenched in my mind that it feels like not striving for something big goes against my very identity. While it might be somewhat unhealthy in a sense, I know just how much more miserable I was throughout school when there was no challenge, so perhaps it's for the better? In a way, I want to make up for lost time, am killing myself for it, but I'm realizing eventually that time lost is time lost, and nothing can be done about it.
Combined with all of this is an insistence on not giving up, and a refusal to accept that there are things that can not be learned. Whenever someone says you can't learn something, I become bent on proving them wrong. And here's the thing, I usually end up learning it fairly well in some way. But the fact that others said it was impossible sticks in my head, and it becomes a moving goalpost. For example, saying "adults can't learn math" (not really true, but stick with me) can mean that adults can't figure out how to do long division, or it could mean adults can't figure out Riemannian Geometry or something if they didn't start as children. When long division comes to you easily, and so does calculus starting as an adult, you wonder -- maybe I'm just average and I misunderstood what it means to really understand math. I don't really understand math, I just know some easy tricks to calculate derivatives and integrals. But in your mind, you still can't get rid of the belief that adults can't learn math.
I know it can be frustrating to hear me ramble about this, because it seems like I'm refusing to accept offered solutions, but I hope I'm able to convey that I'm not countering the suggestions just because I'm trying to be dense, but rather because I would be interested in hearing something which goes deeper and which is more nuanced. For example, it is trivial to state that effort is necessary and we've all heard the proverb since we were six years old, but what should you work hard for? What constitutes working hard? When do you know something is impossible even if you work hard, and when should you quit? It is the setting of priorities in your life which is the really difficult thing to do, and where you would actually need help. I mean, if someone was sitting on the couch playing video games all day, you could ask them to work hard and you'd be justified, but it's hardly reasonable advice for someone already working their ass off and getting nowhere!