Accepting Your Past
"I did the best I could with the knowledge I had at the time."
That sentence and it's variations, are beautiful practices in accepting your past self and recovering from the shame of not knowing what you do now.
However, it is a sentence that should only be repeated to yourself in private. You may share it with others when you see them struggling from that same shame, but it should not be used in a conversation to justify your past actions and the harm it did to others.
They already know you did the best you could. They don't blame you for not knowing. You don't need to remind them.