On a little bit of a different note, I'd add that getting a good night's sleep and making room in my day to work out for an hour or so dramatically increases my productivity. Not necessarily my total hours - but my highly productive hours.
Assuming that you're in a position where your results are generally limited by your own abilities, if you can work things so that you have 3-4 1 hour blocks in which you do nothing but focussed production you'll likely find yourself far ahead of the pack. At that point, feel free to give yourself those other "working" hours back rather than using them to twiddle your thumbs on a keyboard.
Answered 9 years ago