Don't take life too seriously! My cousin is easily offended when the topic of conversation goes to age because people always think she's older than her actual age. I don't want to be like that, and unless you want for that to happen, theeeen don't take life too hard!
Choose your battles. And always remember what Paolo Coelho is quoted to have said non-verbatim: success is being able to sleep at night with your soul at peace.
Relax and take it easy. It may sound hackneyed, but these are things all young people need to hear.
Don't rush things. Anything worth having is worth waiting for! :)