Staying Sharp
caffeine: Some points about this:(0) There is no maintenance diet.  Getting sharper is necessary to be sharp.  If you're not getting smarter, you're getting dumber.(1) Reading is NOT the solution.  Much as regular masturbation does not much improve your sexual technique, regular book/article/blog-reading does not much hone your mental edge.(2) You got sharp => you know how to get sharp.  Do the same thing.  In other words: figure out the next piece of physics that really interests you.  Get the classic research monograph.  Attack all the thorniest problems with vigor and delight. Repeat.(3) Time is an issue - you don't have much of it, and what you spend it on at the moment is worthwhile.  I think if you devote some small period of time each week (after dinner on Sunday evening, say) to practicing (2), you will come to look forward to that time each week, and will feel your clarity return.  In the end, the key is regularity.