Yeah... I know what you mean. Sleep is pretty weird.
For a long time (at least a couple of years) when I was still living at home and quite depressed I slept very little, yet never felt as though I was tired even after playing videogames 'til sunrise and beyond. I think I kinda prided myself on not needing much sleep.
Then I moved out, and wound up sharing a house with a group of people who (at least when I'd just recently moved in) tended to go to bed very early, by my standards. Probably ten or eleven PM. Not wanting to go wandering noisily around the house when everyone else was trying to sleep, I started going to bed then, too- and after just a day or so of that I felt amazingly good, brimming with confidence and vigour that I never normally had.
It was then that I realised, all that time with my terribly unhealthy sleep pattern, I
had been tired- extremely tired, I just never realised it because I had nothing else to compare it to. I'm definitely well aware of the benefits of having a set sleep schedule, and I've forced myself into one a few times in the past, it's just that my last few attempts have failed due to lack of willpower and various distractions.
...That was kind of rambly. Oh well.
I should really get around to starting up my 'go to bed at 11 pm, stay there until 7 am' routine again. Usually gives me some gnarly nightmares the first couple of nights, but then I start feeling really good.