I don't know if this is helpful or not but i'll throw it out there.
I have been married twice. My first relationship was violent. I was quite young. I stayed married for a long time. It never occurred to me initially to not marry this person (again, young and lacking experience and apparently good judgement lol). I really did care about him though, you know the story.
So divorced and moving on, I still trusted my judgement, I didn't have those self doubts (those would come later after 2 more relationships).
Up until now, I have looked at it this way. Instead of saying - oh what did I do and how did I trust that person and how did I make that decision etc, I decided to just move on. Wiser from the experience.
I don't see them as mistakes as such, I see them as part of my life. If that makes sense? Neither really good nor bad, it is just part of my life, part of my learning/experience.
I would compare it to deciding to move to say - Oregon. Beautiful State. You pack your bags and move! Life is good for a while until you realize you miss all your friends in Colorado, you miss your old job, it rains all the time. You pack your bags and move back!
Now, was the move to Oregon a mistake? Perhaps. Is the fact that you have to ask for your old job back and you spent all that money moving really annoying, yes! But how would you know that if you didn't do it and didn't you learn and didn't you gain experience and the next time you decide to move you are going to maybe book a two week holiday there first. Not being overly cautious, just applying what you have learned.