> At some level of complexity we learn "too hard for me to integrate by hand" and also stop learning how to perform more and more complex integrals. We stop. Where is the most productive place, to maximise useful learning, to stop?
I preface this by saying I find math very difficult. However, it is the struggle to understand in mathematics that leads me to understand the concepts. It often seems too hard, but I found that if I stuck at it I actually started to understand what was going on.
Not popular advise, I realise, but those who can stick with it seem to find maths almost fun, despite the pain.