I don't think regrets are necessary at all. No mistakes means no learning. But of course mistakes -/> regrets.
If you make the best decision with the information you have at hand you shouldn't regret the decision you make. Retroactively the decision can turn out to be a mistake, but those mistakes you can easily accept: at the time you believed you made the right decision.
There's no need to second guess yourself, beat yourself up and ask "What if?". You can make a decision and if it turns out to be a mistake, just say "whoops" and move on.
There's a difference between not wanting to do something again because you learned that it was mistake and regretting having done it in the first place. I've made plenty of mistakes and learned to not do that thing again, but I don't regret them. After all, had I not made those mistakes, I wouldn't know that they were, in fact, mistakes.
I think I understand what you're saying. For example, I didn't know I had a bad back until I tried to lift a heavy monitor once and it hurt a lot. Rationally, I know that I could not have known before, and it's good that I've learned. But instinctively I still get a shudder whenever I contemplate lifting something heavy, and I think that's been preventing me from hurting my back again more than any rational thought.
Regretting things you have done is different to regretting things you haven't done.
If you regret nothing you have done at the end of your life it probably means you never made any serious, life-ruining decisions or you were incredibly lucky. That in itself is something to contemplate long and hard (luck or tragedy). Significant risks come with significant ramifications and sometimes taking a risk doesn't work out. Perhaps the question if you never took such risks is would your life be any different if you had taken the riskier path.
You don't walk away from accidentally killing someone or destroying their life with just a "whoops" unless you have something seriously wrong with you.
If you make the best decision with the information you have at hand you shouldn't regret the decision you make. Retroactively the decision can turn out to be a mistake, but those mistakes you can easily accept: at the time you believed you made the right decision.
There's no need to second guess yourself, beat yourself up and ask "What if?". You can make a decision and if it turns out to be a mistake, just say "whoops" and move on.