It is very safe, people far younger than you do it all the time.
If it is your first time the best suggestion I can give is let those working the flight that you are a little nervous and PLEASE do not be embarrassed to say so. When you tell them that they will treat you wonderfully, check in on you more often and sometimes give you a few extra snacks. :)
I even know some kids who were moved up to empty seats in first class.
Relax and enjoy the flight.
yeh im a teen and i do all the time since i was like a baby lol
No don't wory all the way there there will be people to help you like security and flight attendendants