Sleep is incredibly important to your personal productivity. 8 hours per night is sufficient for most people, but you might find less is better for your body.

The key is really in maintaining a regular sleep schedule so that your body can really get used to the cycle of work and rest. Numerous successful entrepreneurs have written to a great extent about sleep hacking including Chris Brogan.

There's a great TED talk by Arianna Huffington below that can help you better understand the importance of sleep if you're one of those people who think energy drinks and double espressos are the way to go.