Yes, I'm in a much better place than I was 30 years ago (had a really poor self-esteem as a teenager/young person due to my mother's psychological and emotional abuse).
I trained as a counsellor and then as a psychotherapist - during both of those processes you need to undertake your own therapy and also really delve into yourself as a person. I was a completely different person when I finished - in a sense, you unpack everything then build it up again in a new way. Although I no longer practice as a therapist, I think the training and accompanying therapy was the single most valuable thing I've ever done for myself and my family. (I was a much better parent, etc. afterwards.)
For me, the key is to learn how to value yourself - to give yourself the approval and love that others might not have given you in your past and might not be able to give you now.
As to fitting in, etc., I really don't 'fit in' most of the time but I just don't give a fig. I don't even try because I've learned that it doesn't matter. (And through talking to my clients, I realised that actually, most people feel that way a lot of the time.)
I'm also NC with my mother, not because of the way she treated us in our childhood (I know she did her best, it's just that, unfortunately, her best was abusive) but because even though she's now elderly, she continues to behave in the same abusive way and I choose not to inflict it on myself or my children.
It's hard work to replace those negative voices with positive ones, but you can definitely do it. You just need to find an approach that works for you, whether that's therapy, coaching or something else.