My ideal sleep time is from 12am to 9am, so I guess 9 hours. For some reason, I tend to feel very sleepy if I wake up before 9am, even if I have slept for 8+ hours.
A bad habit I need to change is procrastinating sleep, it would be 10pm, and I would think "Hm I still have enough time to do other stuff (Like homework, hobbies etc), then I blinked and it would be past 12am. I am worried staying past midnight would be a slippery slope that I would sleep later and later, so I'm trying to fix that habit.