When I was in college, my sleep cycle got really bad. I've got a very sensitive sleep clock and it would go out of wack in no time. I would start going to sleep at 7-8 in the morning and wake up at 10AM and then be wasted all day and not be able to sleep at night. It was all fucked up. I realized that it was messing with my life and it was time to grow up.
Since then, I've stuck to a pattern and haven't changed it more than a couple times a year in the past decade or so. I go to sleep at around 11 every night and wake up between 5-6 every morning (depending on weekday vs weekend and other factors).
Go to sleep at the same time every night and up at the same time every morning. For me, it is a religion because I know how bad it can get and how quickly it can go downhill.