On the other hand, now I am 32, and when I look at back at my 15-year old self, I just knew everything back then. I am only regressing since then in all ways
Maybe in feeling but certainly not literally. A 32 year old working in a field is going to know far more than their 15 year old counterpart. Of course you may be getting into the "I know that I know nothing" regime. While your 15 year old self subjectively thought they knew everything.
The Best Lack All Conviction While the Worst Are Full of Passionate Intensity