I did just what I did and that is likely the best I could have done knowing what I knew and being who I was at that moment in history

That's pretty much exactly what I tell people when they're stressing about how they should have done this, that or the other thing in the past knowing what they do now (some of them are at least able to say if only they had known what they do now). And add that as long as you're doing the best you can with what you know right now, while it would be nice to have the future knowledge, at least you were trying now instead of...not right XD