(This became long whoops sorry)
I wish I spent more time with my childhood friends from ages 11 to 15. We all started secondary school and weren't gathering outside as much as we used to anymore, but at least they made attempts to get me out of the house by stopping at my door and asking me. I always refused, both because I was becoming more of an introvert home hermit and often because I just was lazy. We drifted apart in these years and that was entirely my fault (arguably, my mother's disapproval of them also was lowkey in play here).
Funnily, I only realized that when not me, but a then-friend of my had a dream. She told in class that she dreamed her own childhood friend came at her door, but that she didn't hang out with him because she was lazy. She said she regretted that and that made me realize that it was entirely my own doing. It felt like it was too late to restore friendship, even though they (they're brothers) live a few houses away from me. I was just so anxious about going to their door and asking them to come outside - it was one of the most irrational fears I had but I had it ever since I knew them at age 4.
Aside from that, I thought that it was too late because it had been years since we hung out together. I'd sometimes see them outside with some other people from the window (of course, they got other friends too), and that was always very disheartening to see. It continued to be a heartache until one day, when I saw both of them outside once again, I decided - no, this friendship must be relinked and it is my responsibility to do so. So in the most dramatic way for such a non-dramatic situation, I ran outside (making sure we wouldn't miss each other) and talked to them again. It felt awkward as hell to me, as if I suddenly didn't know how to talk to them anymore after all these years, but it was enough to rekindle the friendship. We exchanged numbers, asked each other (especially I to them) to hang out more often, and included each other in each other's lives again. We returned to the great friendship we had all along.
Nowadays, about 4 years later, they are still one of my closest friends, and along with two others from the neighbourhood we have a small friend group (mainly centered around Pok?mon). I honestly feel beyond blessed to have them back in my life; they are like a constant factor as I move through several life phases in my life, and it's very comforting to have such a close, but chill friendship with them. This specific happening taught me that I shouldn't let my friendships with people die - I should reach out to them and put equal effort in the friendship, to make sure it lasts. Though there were several more factors at play here (Pok?mon actually being one), it was 100% my fault that this happened. I do not want that again, especially not with them.
The only other people I regret not spending more time with are my aunts - and within my family as a whole - back when I was younger. Though I always enjoyed family gatherings, I did usually hide upstairs (puberty + games are fun). Unfortunately, now that I would like to spend quality time with my family, the ties have worsened due to several fights and unresolved tension, so the family feeling I had years ago is no more. I am sometimes envious of my sister that she was able to fully experience the family while it was still intact and fun, because I never will.