How to get over being jealous?

My boyfriend said something a while back. We got into an arugment over something. He said he simply wasnt going to leave me due to my crazy life.

But here is what I've been having a hard time getting over he said "It's not like your on drugs, if you were doing them I would leave you. With my ex (she was a druggie) it didn't matter because I was madly in love with her. And the only reason we are together is because she left me, and fucked another guy. So in fact you should thank her for us being together. Because that's the only reason we are together."

It's been a year almost a year since that was said... It still gets to me.