Mentally start imagining this person not as a human but as a toad. Turn him in your head from human into snake or toad or octopus, and in your head stop imagining him as a human. The more you take control of constantly rewinding and replaying the "instant replay", the easier it becomes to change the channel of interesting things in your head and move on. Whenever this person comes back into your head, visualize them as a toad or an octopus, but, be firm, say "no" in your head, and visualize something else right away. I start singing punk or metal songs in my head to get the crappy stuff of being a victim out of my memory banks. My evil sister was born in the year of the dragon, so, now I visualize her as an ugly dragon in my head and when we have arguments to this day I visualize her as the ugly dragon breathing fire and having never had a boyfriend and it equalizes things and I can then get her ugly face out of my head faster. There's like a million other things to think about than this one toad in the world. It is springtime! Start looking at flowers. Look at the baby animals in the farms. Look at the butterflies. Go to the concerts in the park and listen to live music under the stars. Go to the lake and look at the water and the fish and real frogs in the water. Look at the tadpoles and the minnows and the dragonflies. Look at the clouds and the stars at night and get this fool out of your head. Look at nicer people and look at funny things that make you laugh, and look at him like a toad and laugh at him for being a frog who tried to become a prince but failed and is still a frog and be done with him. I did. Good luck to you but go and DO.