I've just done a lone flight, i'm 15 and it was 14hrs total with a plane transfer halfway >_< I'm alive lol, so you'll be fine
My first flight alone (the worst was the exchange, i was scared i'd end up in like..australia..) and it wasn't awful. I'm glad i'm coming back with my family though!
I stupidly left my book at home but they all have those little screens so i ended up sleeping 4 hours and watching 4 films lol. The rest eating or playing tetris (on the screen) or playing hangman with the chinese girl next to me.. didn't go too well. She understood about 5 words of english! No idea what i'm going to do on the way back, i doubt they change the films so i'll be watching rubbish!