I was an attractive child, so when I was young, I never gave appearance a second thought - which meant puberty came as a shock as I filled out at 11-12 and got problem skin and haywire hair. I went from being active to being quite introverted, because suddenly I was all too aware of my "flaws" and how people reacted to my new appearance.
Then when I reached 16, I started gaining control over my own routines (yes, I had strict parents too) and transformed into a person who made an impression and was popular with the boys (and girls also, as I wasn't perfectly pretty). However, this brought its own problems, as I started getting too much attention and ended up with stalkers. I then retreated away from making the most of myself, into the world of putting weight on and wearing baggier clothes.
From 22 onwards, adult life also brought the mundane reality of having to work in an office and fit in and look sensible, so there wasn't much room for experimentation.
Now that I'm thirtysomething, I can look back and realise it all starts from within. I now have the personal authority to be able to cope with any person who wishes to undermine me. Developing that authority does take time, but you will gain it. No-one has it at 16 - it's built day by day from all those bad moments you go through. Your reward is something good - strength.
And don't forget - if you didn't win any prizes for beauty when you were a teen, there are still many ways to triumph. I've lost count of how many people I know who have descended into a thirtysomething slump, losing their looks, while I remain fresh and lovely, because I looked after myself. We all have our moments in the sun.