Your teens and early twenties are happy, confusing, exciting, and exhilarating all at the same time as you learn about life, yourself, and others. Those years are full of extremes - one day is the best day of your life and the next is the worst. You are definitely on a emotional rollercoaster.
Once you have exited the bloom of youth you often look back only to wish you knew then what you know now. You truly begin to appreciate the saying, "youth is wasted on the young" because while the advantage of youth is vitality you are missing the wisdom to use your vitality wisely.