I broke up with my highschool sweetheart last year and felt great at first. Then 2 months later i suddenly missed the shit out of her. She was all i could think about and i ended up hamstering away and getting back together (bad idea I learned my lesson). Anyways we broke again and I felt great (missed her ofc but still great) and just like clockwork 2 months later shes taking over my mind again and its really fucking with me. Is there a reason for this?

EDIT: this was the only girl ive been in a relationship with. Is this just my mind starting to accept that shes actually gone or something?