Can strong Lust attraction/pion turn to sadness?? normal?? help 10 ptz best?

There was this guy I had a crush on and it was all ual..feelings I mean I would fantasize about him and ..even would say his name and picture his face, While with someone else.. Now that I got rejected by him.. I cant seem to stop crying/thinking about him. It's no really ual anymore it just sadness..But it comes sometimes. I thought this was all ual why do I cry?? is this normal I still have trouble movin on.