Staying emotionally connected to someone who is not good for you does not allow you to experience the freedom of discovering who you are without this person. In my book, Secrets of Happy Couples, I write about 'The Alone Stage' when you are between relationships and how important it is to take that time to really discover yourself. You cannot do this when you are still emotionally in a relationship with your ex.
Free yourself to explore what you really want in a partner. Discover your non-negotiables — those things that are absolute deal breakers for you. You shouldn't have too many of these, perhaps three to five. But once you know what they are, never compromise on them. Once you recognize one, get out of the relationship.
Also, make your list of what you really want in your partner knowing they aren't dealbreakers if a person doesn't have everything on the list. It then becomes easier for you to keep yourself from investing in relationships you know are not going to end well. Then, ask yourself the hardest question of all, "Am I the person my "perfect" mate will fall for?" If the answer is no, then it's time to continue on the self-improvement path until you become the person you need to be to attract the person you really want in your life.
I know it's hard. I know you have caught at least some glimpses of the person you really want in your ex, making you believe a true transformation is possible. I'm not saying people never change, but I am suggesting that waiting around for a miraculous shift in behavior or personality is not a great investment of your time. How long have you already been waiting? Three years? Five years? Ten? Are you willing to wait ten more or are you ready to take charge of your life again?
When you make the commitment to honor yourself, you will realize you're being held prisoner of your own misplaced loyalty. Put your ex in the past where she or he belongs. Take some time to discover what the relationship taught you. It is never a mistake to love someone, but when it's time to move on, help put the relationship in perspective by articulating what you gained from the relationship. There was a lesson, a benefit, a gift or an opportunity that your relationship with your ex afforded you. Zero in on those lessons and gifts. This balances the pain of the loss of the relationship with all you have gained, giving you permission to move forward to the next great adventure.