Very true. Often people develop coping mechanisms to get through traumatic experiences, but those coping mechanisms are also often dysfunctional and don't serve us well in life afterwards. They need to be changed later on, and that's hard, too.
To forgive myself, my therapist taught me to honour those coping mechanisms, because in a lot of ways, they saved my life. Once you make peace with that, they are much easier to change when they no longer are serving you.
I like your thoughts on teaching children to defend their own boundaries.