Do something completly different which empties out your mind. For me that is going for a run, others play the guitar, just try and get away from the computer fo

Do something completly different which empties out your mind. For me that is going for a run, others play the guitar, just try and get away from the computer for a good while before trying to sleep. And I second the note about discipline. Define your working hours and stick to them. If you can't do it, get yourself a faimily: they'll do it for you :)