Um, five years leads me to... Third year of secondary school/ninth grade? There's not much I would change about these years. I was already accepting my sexuality, my social life was good, and there was not much that really went wrong. There are two things that specifically come into my mind, however.
First, I would never go on our school trip to Spain. Instead, I would've gone to Italy, as it would've saved me a major fight with my friend, arsehole teachers and an overall bad trip. I only have bitter memories from that trip - wanting to redo my Spain experience is exactly why I'm going next year.
Second, I would not follow the rest of the crowd and bully that girl. At that moment it truly felt like I was doing the right thing by not interacting with her just because others were telling me she didn't like me or whatever. I should've not gone along with their bullying and instead interacted more with the girl herself on non-hostile terms. When I realized what we were doing was essentially bullying, it was already too late for her...
After she was gone for a year and returned, I made sure to get on good terms with her - which I did, but I never got to apologize for the way I treated her all those years before. At first the others were friendly with her as well, but once it came out that no one essentially cared for her or still disliked her, I felt even worse about what we did. I decide to let whatever we had build die down once I left secondary and she still had one year left. To me it felt better that I, as someone who was part of the shit she went through, did not interact with her anymore. Ironically I've been bullied as well, and I have no desire to ever interact with that ass.
I hope she's in a much better place now. I won't ever have her forgiveness (she said so), but I am in no way desiring that. All of this is the only big regret of these last five years.
One additional thing would be to push furhter to interact with the partying crowd, because I really wish I would be invited to parties now orz. Then there's also that I wish I could do something against me having to follow economics in the last three years of secondary school, but there was not much I could really do because my parents were forcing this choice on me. To put in perspective how much I suffered because of economics: it gave me trichotillomania.