I bumped into a high school classmate who I hadn't seen for more than a decade. She had just turned 30 and we were joking about how much "progress" we've made since high school. When are we going to finally become grown-ups?
For the past year, I have had the privilege of being back at university. Most of my classmates are 18 years old, with all the adorable flaws you have at that age.
It's hard to notice progress day by day, but it is happening. I only appreciated the progress in a computer lab recently, when a bunch of rather stinky undergrad Computer Science students strolled in. Although there was no evidence of physical activity (this is Computer Science), it smelled like there had been a lot of it.
I have made a tremendous amount of progress since I was a stinky teenager. I'm sure you have changed too. I bet you're a kinder, stronger, nicer smelling person now.
Trust that you are better today than you were yesterday.