Tired? The importance of letting ideas marinate and percolate through sleep
nytimes.com
nytimes.com
I am glad you realized you needed your share of sleep.
Edit: here's a wiki article about the topic: http://en.wikipedia.org/wiki/Sleep_and_creativity
On the other hand, some of my finest moments of clarity have come after all-night cramming sessions. It's as if you fatigue all the usual pathways and are open up to entirely new ways of seeing things.
Don't confuse working on a problem for a long time, understanding it very clearly with having the idea in your head and regurgitating a solution in one long stint. Woz emphasized this in his 2005 Startup School talk. Understanding an idea so completely in your head you can simplify it no more.
Every once in a while in the past, when I was working on my own project, I've done it to the point where I would sleep from 2am to 1pm, and the next time living in the dark for a day due to going to bed around sunrise (5am) and waking up at sundown (6pm), and so on. Eventually, I would have a normal schedule again. :) This was when my only focus was on writing code for my software and working out, period. Since my software became better every week, and I grew stronger, bigger, and faster as well, my goals were pretty much met and I was happy.
I like my current life as a student, due to the social aspect of learning from, and working with, others. But I am nowhere near as productive at developing my own software on a daily basis nor working out as I was when those were my only two goals. However, I understand that it has only been a few weeks, and I will be able to figure out how to introduce software and personal development into my schedule as I get more used to the demands of my classes. And even though I won't be able to dedicate as much time as I could before, I have the experience and confidence to get in shape and create software more efficiently, as well as the benefit of a being around lots of potential users.
So sleeping did not impede him working 24 hours a day. It actually helped.
Other problems demand several passes of experimentation. For those it's easier to try a quick test during the day, think about it while doing other things, and then wake up with the (possible) solution the next day.