There is one instance in my recent memory I wish I had behaved differently.
Not too long ago I was doing namaz in public the way I've done so many times before. This time was different. Someone confronted me when I was doing namaz. I wasn't scared at all. It wasn't confrontational, but the other person was definitely adversarial. I was civil and nice enough and I even said, "have a great day" at the end of our interaction. I regret not being outwardly nicer. I have thought about what I regret and what I still think about before. In my head, I was nice, but he didn't know that. He could have easily interpreted what I thought was pleasant as me being sarcastic when I said, "have a great day". Mostly, I regret not taking an opportunity to have a good interaction and possibly brighten someone's day.
Taher, learn from this. It's not enough to think it. Do it and make it clear.