If we learned from that past & have made changes to our life, then we need to look at it as a learning process & a growing process rather than with regret.
I made a bad choice in my marriage & stayed in that marriage for 33 years before I walked out on it. I could have wrapped myself up in the regrets of either choice BUT I have chosen to start my life over (I was 54 at the time 15 years ago). Instead of regret, I am thankful because I love my life now & that change & growth I have made over the last 15 years is based on what I learned from my bad choices & good choices during those first 54 years of my life. I choose to focus on the positive NOW rather than wallowing in past regrets. Makes for a much more enjoyable life