forgetting?

I've had an on & off relationship with this guy for 3 years , he was my first attachment & love. I don't want to continue to be there for him because I feel that he thinks he can do anything he wants & everything is going to be ok because I'm always going to be here for him no matter he's mistakes. what can I do or say to show him that I'm over him . I'm really trying . please don't judge .