Three things come to mind for me. 21 years ago I met my wife. I was seeing my best mate's sister-in-law at the time, and broke it off with her to pursue the missus. At the time nobody was happy with me. I lost friends (who had planned out this future for me with the other girl). My parents could not understand why I left a nice enough girl for a divorcee with two kids who was a couple of years older than me. But I just knew that she was the one for me. And in the process I gained two step-daughters who have now grown up. Spent all day Saturday with one, and she gave me a lovely Father's Day card; came home and the other one had sent me a gift via Amazon. And of course, our own two followed and I spent most of Sunday building a shed with my son, who is off to uni in September. Do I regret that choice I made, and the friends I lost? Not for a second.
Second, like many folk on here, was changing jobs. In 2013 I was in a job that had a wonderful job title and from the outside looked like an amazing job. But I hated it, and I was bored. I applied for a lectureship, got it and this really is the job for me. I actually have a job that can make a difference in people's lives. I posted before about this, but a few weeks ago I managed to get a guy to graduate when the Chair of the exam board had decided that he was to resit a course. A full year extra at uni to sit an exam he missed through no fault of his own, graduating next year in a room full of strangers, and losing job opportunities now. Took me a full day, and arguing the finer points of some obscure uni policies to win my point, and yesterday he graduated at the ceremony with all his friends and is off into the world with his (hard-won) degree.
Finally, 26th March, the last day I saw my dad when he was terribly ill. He died the next day. All I'll say is, we left nothing unsaid. My last words to him were that I loved him.