ex-g/fs suck

My ex and I are trying to be friends. That means trying to be honest with each other which is not good emotionally with either it seems. Her best advice to me came tonight was with writing my thoughts and venting to try and let those emotions out and help me get over them. So here it goes. My ex when I first met her was unhappy with her life and I kept telling her that she needed to learn to be happy with herself before she opened up to anyone else. I tried to make her feel better about herself and build her self-esteem. What happened was when I opened up to her like that I started to lose myself. I slowly built my happiness around being with her and her alone. Then I started to resent her for growing emotionally. I started to treat her like crap in public and put her down because of this jealousy. I thought that she would always be that broken girl who needed me around to be happy. I have been thinking about how I treated her and how I put her down in front of her friends and I hate myself for it. After I started acting like this she started to treat me like a emotional punching bag. I now understand why this happened. I understand why we would never work together but there is a part of me that still wants to be with her. She has now moved on and that also hurts because I still think I need to sort out my feeling for her. Now as of today, fear has grown in my mind and I am scared of opening up to another the same way. My personality won't let me go halfway with anyone. You either get all of me or none and that is not good if you ever want to find anyone to share your happiness with. The scare is based on how I treated my ex. I feel like no person should ever be treated that way. My ex says that you may get broken many times in your life before you find someone that will put up with your bullshit. Those of you who have found happiness in your life are the lucky ones, I have always thought that everyone deserves the best of life but I don't think I do. I need to find a way to change myself and not hurt anyone with opening up myself. I am trying to grow as a person but it is hard and I need to be willing to do so. The fear comes from the feeling that I will never be able to change for the better. This is my first post and I hope that writing will help alleviate my feelings of self-doubt. Thank you if you read this and thank you for advice if you give any. I will probably post once a week or whenever I feel a strong emotion.