The one and only regret I have is sending a previous GSD to the wrong trainer in the '80s, on the advice of a policeman. They who ruined him, and turned him aggressive to children and I had to put him down (no choice at that time). The only good that came out of it was that I became a trainer myself. But it hurts to this day and hope to see him at the Bridge to apologize for my failure to protect him.
The rest of my life has been without regrets. Some things I wouldn't repeat but they made me who I am today, so no regrets in these.