Sleep

Sleep is very important. You probably hear that a lot from your parents and I may sound like them too, but it is true and you should listen. Everyone has a curfew - set bed time - or a time they normally go to bed. Mine is 10 pm. But just because that's when you go to bed, it doesn't mean you go to sleep straight a way. Even though I go to bed at 10 pm, I normally only fall asleep before 11 pm. I may not be sleeping in that hour, but I am still resting - lying in bed NOT using any devices.
Last night I was up two hours past my bed time trying to finished the last of an assignment, I got it done at midnight. Now, because I'm not used to staying up so late I have been extremely tired all day long. A few times I was almost asleep and I think I was for about five minutes at lunch.
Everybody needs sleep, some more than others. Don't stay up late. Being a teenager doesn't give you the automatic right to stay up as late as you wish. Just because you're a teenager - or adult - going to bed early doesn't mean you're weak or whatever, I think you're the responsible peeople because you know when enough is enough.

Fun fact: the more you sleep the taller you are.