Living in regret isn't living, per se. As your post mentioned, unhealthy and you've a desire to move forward. Sorting through what it is about her that drew you to her, may be symbolic of certain qualities, that you maybe able to add to your own persona and perhaps seek out in another, for a relationship.
Hopefully, you're able to establish a more here and now relationship which may help relieve the built up fantasy effect of the girl, from your past.

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