Maybe 10 are too much, Only three decisions come to my mind.
Decide to never get into drugs, many of the people who have the same age as and live on my neighborhood are involved in drugs and vandalism now, and I feel really proud of not being one of them.
Study english, this let me now other people's opinions and views of life. Languages, besides is like my little big proud, I learn them really quicky

. Now I'm 3 cycles left to graduate.
Decide to be entirelly interested in music, well I' m not a big music searcher but thanks to my eclectic tastes I can help or recommend other people songs when they want to think, dance, etc. And also thanks to the music I have a way to express myself.
Great question BTW