Are you the type of person that fills every moment of your life? Busy, busy, busy... Some of us pride ourselves on being busy as if it somehow means we're successful... WRONG! A busy person may or may not be successful, but I can almost guarantee that they are EXHAUSTED! Believe me... I understand...
I am one of those busy types of people, scurrying about, trying to get things done. For a while, I even tried to train myself to live on 3 hours of sleep per night... In the wise words of @Kyle, "That might not be the best idea.". He was right. Weird things started to happen after about a week: random hallucinations, waking up in strange places, etc.
I have come to the conclusion that getting good rest is pretty important.
Don't get me wrong, it's good to strive, to work hard, giving everything you have in pursuit of a good achievement. If you want to accomplish anything, you will be REQUIRED to work hard. Just remember to take a break once in a while. Shift gears, enjoy silence, meditate, pray, sleep, something that helps you recuperate. Just be sure to detach from your task so you will be able to come back with a fresh perspective.
Taking a rest is not laziness. In fact, we get some of our most important ideas during these times. With that in mind, stopping to do nothing may be one of the most productive things we do!!
Just be sure to get going again afterward. =)