you and Cupid are enemies because your an anti-cupid so your two didn't like each other at all obviously and it was forbidden for a Cupid to love an anti-cupid or an anti-cupid to love an Cupid...

one day you both were in the clouds and were arguing and shooting people with your arrows from above like always... When he accidentally shot you with one of his arrows

Cupid:"oh... sorry..." he smiles slyly