I Recently Lost My Gf But I Do Not Understand The Reason

i recently lost my gf but i do not understand the reason she told me there wasn’t a “spark” in our relationship but i do not get it i tried my best i didn’t even hardly talk to anyone else but her but i think she just lost interest and now i just feel lost my grades are terrible like very bad and everything was just a down fall after she left me and now i’m being told i have attachment issues