How to Deal with Feeling like a Failure

Do you guys ever wish you could just redo highschool? I've been trying to get through this feeling but it keeps nagging in the back of my head.

For context, I'm a freshman in university, recently graduated high school, and I'm feeling like I missed out big time. I used to be homeschooled (starting in 5th grade) due to my mom thinking my ADHD was too much for in-person learning, and since I was young, I never really thought school was important or cool or, really, anything substantial.

That is, of course, until I begged her to put me back in my Junior year. I fucking soared, dude. Near the top of my class for those last two years I was there. 4.3 average. But then my grades came out for the entirety of my highschool career, and it felt like none of my efforts even mattered, because the grades I had gotten back in homeschool were abysmal. Sure, a 3.8 will get you into a lot of schools, but none of the schools I truly wanted to get in.

I feel like I shouldn't even care about the university I'm in, I should be grateful that I'm even given this chance in the first place, it's an amazing school and it has damn good benefits, but I still regret so much. I keep wondering what I could've been — where I could've been — had I come back to school just two years earlier. I could've gone to places like CMU or MIT. I could've gotten a free ride. It could've been great. It could have been perfect. I'm struggling now to pay for my tuition, imagine how much easier it could have been had I just gone back two years earlier?

I feel so selfish for feeling like this but I can't ever get it to stop. I don't know how to get rid of it. I just want to learn but everywhere I turn it's Harvard or Yale or some other school that I WISH I had the chance to go to. I feel like a failure.