In later years, he became relatively isolated; the development of intuitionism at its source was taken up by his student Arend Heyting. Dutch mathematician and historian of mathematics Bartel Leendert van der Waerden attended lectures given by Brouwer in later years, and commented: "Even though his most important research contributions were in topology, Brouwer never gave courses in topology, but always on — and only on — the foundations of his intuitionism. It seemed that he was no longer convinced of his results in topology because they were not correct from the point of view of intuitionism, and he judged everything he had done before, his greatest output, false according to his philosophy."
I think the lesson here is about "tunneling". In Brower's case he was so convinced of a worldview that he felt that everything must be filtered through this lens. He lived his philosophy, which is admirable in some sense.
I often fell, and still fall, into the trap of becoming so engaged with something to the extent that I forget everything else: sleep, work, even other people or pursuits I cherish and value, if I would remember them. Often at school and work I'd become obsessed with some puzzle, question, or thought, usually of philosophical or mathematical nature, and squander what little time I had. It's hard to look up when you believe that you're on the verge of some breakthrough, even if you've been looping the same thought for hours. Once I do look up, I realize there will always be thoughts, and there will always be things to keep you occupied. Good ideas and apparent "breakthroughs", it seems, are a dime a dozen. It seems it's better to keep your head up: it's the only way you can look forward.
