Afraid of not living life to the fullest?

I’m turning 21 in a few months. I’m probably going to graduate college late and I’m generally a late bloomer in life. I’ve been making some efforts to go outside more and just enjoy life but it’s been hard due to personal issues. I’m going to therapy and everything but I still kinda feel like a 15 year old. I think that’s because I was 15 when COVID hit. The 3 years since I turned 18 went by reallllly fast. And I’m afraid I’m not going to really live my 20s even though I’m in my early 20s lol. But mostly because I heard life moves faster and faster after 21 I think. I guess I’m also afraid I’m going to blink and next thing I know I’m an old lady just slapping my knee and talking about how I regret everything in life because I didn’t live it to the fullest.