When we are afraid of being alone, we become needy. The greatest counterpart to someone needy is a partner who doesn't need us. This becomes a game of cat and mouse with the cat always chasing -- but never catching -- the mouse. If your partner doesn't take the time to nurture you or the other relationships in their life, there is no way you are going to be "the one" to change them. This is about emotional maturity. The emotionally unavailable are not mature enough to sustain any more than a cat and mouse game. If you stay with someone like this, you will feel more alone than if you were single, but your fears of being alone keep you from seeing rejection as more painful than aloneness.
The fear of being alone can trap you into accepting treatment that is far below the standard of what you deserve. (...) Further, justifying and staying in these dead-end relationships only keeps you from finding the right person for you.
(...) If you have closed a chapter with an ex, keep it closed so you can give yourself fully to the new person in your life.