This is why I’ve always tried to get about 8 1/2 hours of sleep. That seems to be the best way for me to get access to peak mental performance. You might well require less (or more), but to think you can do with 6 hours or less is probably an illusion. Worse, it’s an illusion you’ll have a hard time bursting. Sleep-deprived people often vastly underestimate the impact on their abilities, studies have shown.
Like David, I put a high value on sleep. I go out of my way to make sure I get my seven hours. If I don’t, my brain gets messy and less useful, plus the attendant stubbornness and crankiness of being short on sleep.
Figure out how much sleep you need every night and make sure you get it. You’ll do much better work for it.
Also: naps are fantastic.