Regret, I read recently, is a sign that something is wrong, not in the past, but now. Because, I guess, if you're basically content, or at least functioning in the present, you must be okay with the past, you've made your peace, voila! no regrets.
Regret is sticking hard to me. It's the big round decade-ending birthday looming ahead. I look back on all the things that never happened in my life, and aren't going to. I must be responsible, because it is my life.
Time bends backward twenty years, thirty years, and then springs forward and tears a big aching hole in the fabric of the present. Regret.