I also think if you are like me the reason you do badly want it to work out with your ex is not because it was good (because let’s face it, it wasn’t how could it be if someone let us go not once but numerous times after we gave them love & after all the intimacy both emotional and physically )This all stems from lack of self belief and worth. If you don’t correct that you will push away happiness that is to come. You are basically saying to yourself I will never find someone who will be attracted to me in the same way. When in reality there is that someone waiting  and willing to give you all the things your ex couldn’t give but unless you believe you are worthy of it you will fall into repetitive cycle in finding flaws and magnifying the good times with the ex. Each time the possibility of creating something new you will unconsciously pass up all because of the fear of risking it all again and believing you are worthy of a happy ending. Instead you hold onto what you had.