Good on you for reflecting on your part in the breakdown of these friendships, you sound very similar to my daughter and unfortunately she has not been able to look within and accept her part in these relationships and it has left her very lonely and constantly disappointed.
Sometime as parents we do listen to our children and hear them and apologise for our mistakes and try to explain that we did not know what we were doing and we were trying our best and seeking help to improve and once we did know better we changed our behaviour but the apology is not accepted and the now adult child is not able to move on from the past and forgive. Complex relationships do not always have happy endings even when the best of intentions are brought from both sides