Being one of the oldies (egad, 27!) round here, I feel the need to add my two cents to this thread.
When I was younger, I did some very stupid things. I drove home tired a few times, even had the odd nod at the wheel whilst driving home and yes, I did drink and drive about four or five times. But it wasn't until I was 22 (can you believe it) when I finally woke up to myself, in the worst possible way.
One of my all time bestest friends from high school was drving home (around about a fwo hour drive) after just finishing her required hours to finish her university course in Chiropratic practice. She was, without doubt the most level headed, responsible, caring, thoutful person in the world... yet she was killed when she (although never completely proven) feel asleep at the wheel.
I can still remember every detail about the two hour phone call I got the next night. I had never, ever cried in my life up until then and I continued to cry for months afterwards.
I won't drag this out because I am sure everyone has their own sad tale to tell. All I will say is, just use common sense. If you feel fatigue coming on in any shape or form, pull over on the side of the road and have a nap. It doesn't matter if you have a job to go to, an assignment to hand in or an exam.
Every time I go out clubbing, it is always about a two hour drive. If ever I get the slightest bit of fatigue, I pull over on the side of the road. Once I was so fucked up, it took me nine hours to get home. Even then I probably should have had some more sleep.