I'll also add to your comment that the Learning How to Learn course on Coursera is helpful regarding the concept of challenging yourself, as you can enhance you

I'll also add to your comment that the Learning How to Learn course on Coursera is helpful regarding the concept of challenging yourself, as you can enhance your ability to take on challenging topics in a way that is sustainable and truly productive. For example, the idea of working on a problem eight hours a day straight seems efficient, but it's actually better to take breaks and let your mind wander and make neural connections in the background while you exercise or sleep. And instead of perhaps trying to solve a hard challenge at once in a day, such as learning something very complex, it's helpful to comprehend parts of it and spread it out over a course of a week, not unlike how it's better to learn an instrument by practicing a little bit everyday instead of cramming it into one day a week. Furthermore, instead of just jumping for a quick answer (e.g. StackOverflow, forums, answers sheet), it's helpful to try to solve it on your own even if it takes a much longer time. There's a big difference between 'knowing' something because you saw the solution and reverse engineered the method, vs. coming up with it yourself. Some of this might be stupidly obvious but it's nice to know there is science/other anecdotes behind it. That course is something I wish I had known decades ago before I went to University and in the workplace.