The slight pain, which I refer to, is a healthy sort of pain. When it's caused by failure, it turns out to be necessary for a level of muscle (and neural?) growth that exceeds even the good results you're endorsing. So the idea of it deserves at least more than a grain of salt.

Speaking of slight pain ... I welcome a neuroscientist to weigh in here ... I think it's plausible that the minor head pain/ache we feel, after engaging for a long time with difficult reading material, is our sensation of failing to master the topic studied on account of insufficient neural connections. And I think it's even more plausible that this insufficiency stimulates the quantity or quality of such neural connections to improve. Making our brains stronger in the long run. Totally analogous to weight lifting; ideally to the point of failure.