A fairy tale of sorts

Once upon a time there was a girl. She was what we like to call a "serial dater". She was in long term relationships back to back for 8 years straight. One boy leaves, oh well, the next one's right around the corner. Six years into this constant whirlwind of mean, angry, useless boys she met the one. Or so she thought. He was everything she thought she wanted. The strong quiet type. He had good values, good you know, and he was good looking to boot. Up until this point, the girl had never really dated an attractive guy. She thought they were, of course, but most didn't. Until this one.
This boy took over her brain. He moved in almost immediately and was always there for her, or so it seemed. Soon enough things started to go sour. They were engaged 3 months in (too soon of course) and began to plan for happily ever after. Then he cheated. Things were tense and this girl went crazy. Crazy jealous. She couldn't handle the pressure and couldn't trust him again. She couldn't let him go though. No way no how. So she pushed through it. She dealt with all kinds of bullshit. Tons of potential cheating. Five breakups. But she never gave up. In the back of her mind she knew. It would be her and him forever. Then, during a freak blizzard at the end of February (which doesn't usually happen in VA) and right after the girl's dad died, he left. Left and never came back. This girl lost her mind and went on a fury of binge drinking and overall self loathing.
Fast forward to three months later and she met HIM. The new boy. The love her life. The reason she wakes up smiling every morning and the reason she makes it through the day. And now he's leaving too. How does said girl make sure the next one doesn't leave? It seems almost impossible that she could have to feel this pain again. Yet it's happening. It's playing out right before her eyes.
This feeling has to go away soon or I might just lose it for good. It seems ridiculous that I base my self-worth on if someone loves me or not. But it's always been this way. Call it daddy issues. Call it co-dependence. Call it dumb. Either way, it seems like this pain will never go away.