how to deal

Hello my name is Nicki and i have been out of a long term relationship for about a year now. Me and my ex were together for a long time through think and thin. he ended up in rehab for ten months unbenoce to me that he had even taken drugs. but i stood by his side and fought for him. then he came home and everything was fine then we broke up. he left me and now im still missing him i see him everyday and it kills me. what do i do