The only thing that matters is whether you are doing your best. Each individual is unique, and so should be everyone’s benchmark of performance. And you know, deep down, when you’re giving it your all. That’s all you need to focus on.
Sooner or later, you won’t have them, so it’s better to do what you can now than regret it later.
Your best asset is your mind
So go for it. Learn unendingly and obsessively. That’s where the real magic is. The bigger your library (well, the part that you have actually read), the higher you can rise.