> After solving a challenging problem, I solve it again from scratch, retracing only the insight of the earlier solution. I repeat this until the solution is as clear and direct as I can hope for. Then I look for a general rule for attacking similar problems, that would have led me to approach the given problem in the most efficient way the first time. Often, such a rule is of permanent value.

This has been one of my principles all my life, and I was just thinking recently about the fact that I've never seen it written down anywhere. (Also, about the fact that it really is a question of personal style, because I've read through rough work/notebooks from very successful people who don't seem to think that way at all.)