How do I let go of my ex’s ‘future promise’ and fully focus on myself?

Here’s the breakdown. Back in Grade 10, I got into a really high intensity relationship. I gave her my standard of loyalty , which basically means I treated the relationship with exclusivity and directed all my focus toward her as a future partner, rather than just some high school fling (because we related so well, similar career paths, etc.) We were deeply connected, but my life is very full because I'm balancing a 4.0 GPA, provincial level athletics, and a job.

Eventually, the relationship started to act like a distraction that made us both drift away from our actual goals. By Grade 11, the pressure of school and other external forces became the main reason we had to call it quits, since we both needed to focus on our careers. On top of that, she told me she felt like she wasn't good enough for me or the standards I kept. Now, I’m focused on my own growth and trying to stop the memory of who she used to be from distracting me from the person she’s actually becoming today.

there’s one more layer to this. When we ended things, she mentioned that she wanted to 'run it back' in the future once she had her life and her nursing career together. It sounds like a nice idea, but the reality is that I’m moving at a pace that doesn't wait for people to catch up. I have a 4.0 GPA to protect and offers to get , so I can't live my life based on a 'maybe' from someone who currently isn't meeting the standard.

The problem I'm dealing with now is the mental loop of that future promise versus what I see in the hallways today. Seeing her act accessible to everyone and hanging out with her friends a lot (girls AND guys) makes that 'future' talk feel like a lie. I need to know how to stop letting that hope of what she could be distract me from the fact that she isn't that person right now. I’m choosing to stay cold and focused on my own because I can't afford to hang onto a memory while I'm trying to build a career.

Updates
3 mo
When we broke up the first time, it was because of pressure from her dad, but after a six-month break, she came back saying she couldn't even describe how much she missed me. I gave her another chance, but then the external pressures of school and work hit again. Even a month after the second breakup, she was still claiming me as her future husband and telling everyone I was the love of her life.
Updates
3 mo
She talked about me so much over the summer that our friends actually got annoyed by it, and her mom and brother already know everything about me because she never stopped bringing me up. Both times we split, she was the one who initiated it, but she clearly still has these deep feelings. Now, she’s mentioning wanting to 'run it back' in the future like post grad.
How do I let go of my ex’s ‘future promise’ and fully focus on myself?
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