If you woke up as a 16 year old but kept all your current knowledge and experience, what would you do?

Im about to reach 29.
I feel saddened, lost and incomplete.
I've made many mistakes in my life.
Some of it way before I was 16, but, it could be fixed. But I just made it worse.
At 16 I moved out of my home town to live with my grandmother at the other side of the country (not US). Now I think I should've stayed.
I acted like I was a mature person, made adult decisions with a mind of a child, hurt someone and hurt myself, badly. I was a fool, felt genuinely ashamed of myself.

But I don't actually want to go back, it was my life, my own doing. It taught me that in my life I held many useless things (and people) that didn't add to my self steem, and got rid of it.
I never felt exactly depressed, because I knew my errors and what put me in that situation, didn't actually know what I needed to get out, but I knew how to start looking, and I did good.

But with some scars...

Once I was a kid full of energy, laughter and dreams, well, not anymore since then...