I was 18 when I got my S15, 19 when I sold it and over the course of time it was modified slowly to car with over 250rwhp in a light, nimble chassis.
I never had any problems with it as I realised I was PAYING for the car and if I crashed the car I would be PAYING for the repairs.
Things are appreciated a lot more when you have to work for them. Common sense really?