Help getting past it?

It has been almost a year since my old boy friend shoved me from him into a car and left me standing in a restraunt parking lot...We were together for 4 years and I loved him like no other,really first time I was EVER truely in love. The last 6 months he struck up a (what I called..improper) relationship with another women...he said I was jealous and crowding him and taking up too much of his time and so on...he 'left' me on a Sunday and started dating her on Thursday! I know I will never be back with him and do not want to be..but still to this day I think of him(and her too) and all the hurt and pain and shame of being cheated on and treated badly..everyday. Why cant I get over this hurt feeling? How does one do this?