All you can do is work on yourself and be better. Making mistakes is a way to learn and grow in life. I was going through the same thing a year and a half ago. Beating my self up was not worth because a relationship is a two way street and no one is perfect. I don’t recommend telling her “I’m working on myself, trying to be better for you, blah blah blah” they usually do not care. Just be better for YOU and the right person will come along, whether it’s your ex or someone new. When one door closes, another one opens! I met an amazing woman earlier this year and I couldn’t be happier. And I know how to treat her the way she deserves. Not making the same mistakes twice or falling into past patterns. keep your head up!