Yeah, I remember those days of thinking I knew everything and I had the world in my pocket.
Why does life suck? Because when you're 19 (or 16 or 22) you have your whole life and the world in front of you, and then you wake up one day and you realize you've lived half your lifespan, and you vividly remember your teenage dreams and KNOW that you may just die without half the things you hoped for ever happening.