First, good on you man. It's hard (maybe folly) to give advice to someone you don't know, so I'll just share what worked for me at your age to now. Around your age I started to journal. I struggled to start and keep routines and recognized that the routine would be helpful so I stuck at it. I felt like I got to formalize a conversation I was absent-mindedly having with myself.
The other thing I did was attempt to calmly observe your mind and experience. It seems clear to me now (but wasn't always the case) that our continuous experience (an unending stream of now) is a projection modeled from the sensory input of our 'senses'. That model is very good, but it's worthwhile to remember that you are just assuming there is a room behind you. You haven't seen it for a couple of minutes and for all likelihood it is still there, but you confidence that anything is 'there' is just a consequence of all the times things continued to be there. Your thoughts and model of yourself is very similar in that we assume it continues to be there without looking at it, but in this case - you've never actually looked at the thing doing the looking and just assume it has to be there all along because ... I guess it would be awkward :/
A couple of reading recommendations
The 7 Habits Book is written for people your age, but you can equivalently read the 'adult' version titled "7 Habits of Highly Effective People"
I'd also recommend what others have said here about eating well, staying active, learning and reflecting daily (journaling), and deliberately making yourself a little uncomfortable on a routine basis. Also find and hone your art, whatever that may be.