A person can accept regret while remaining careful about the next similar situation.

Regret does not have to be either denied or worn permanently. You can look at what happened, agree that it was yours, feel the weight of it honestly, and then let it change how you behave rather than how you rate yourself. Those are different responses, and the second one is the one that actually protects other people.

Take one thing you still wince about and separate the two questions: what would you do differently, and what does dwelling on it achieve. Write down the changed behaviour so it exists outside your head. Then, when the same shape of situation appears, act on the note rather than the feeling.