Keith Devlin is a mathematician and a writer. Recently David Bindel  offered a pointer to a thoughtful Devlin essay titled "Staying the Course"  that comments on the sad state of modern study habits:
... In my experience, it is rare these days to encounter a student who will spend more than a few minutes on a math problem, let alone the several hours — or more — it might require. Most students don't know what it means to niggle at a problem — to worry it — on and off for days or weeks on end. In their eyes (if they think about it at all), those of us who do mathematics for a living are some kind of alien species, born with a weird brain that finds math easy. We're not, of course. Our brains are not that different from theirs. Any mathematician who says she or he finds math easy isn't tackling sufficiently challenging problems. The fact is, what most of our students don't realize is that mathematicians are not people who find math easy. We don't. We find it hard. The key factor is that we recognize that, given enough effort, and enough time, it is nevertheless possible.
Not that mathematics is particularly unusual in requiring effort to succeed. Most things do. ...
Devlin's commentary cites another current article of his, "Major Advance on the Twin Primes Conjecture" , which is rather more technical and includes the delightful:
Goldston told the audience at his AIM lecture that he had been working on the problem for twenty years, but for most of that time did not expect to solve it, his goal being the more modest one of trying to understand why it was so difficult.