How wrong is it to relish in disaster.?

My ex and I have been apart for a year. Tomorrow he is marrying his mistress. He is 45, she is 30, with three kids of three fathers, and has cheated to get out of each of her relationships. I no longer have anything to do with my ex. and am happier in my new life than I ever was with him< he was quite cruel to me. I find my self enjoying the thoughts of him marrying her, and what will probably happen to him in the next years to come. I am relishing in what may be his down fall. I really don't like this trait in myself, but the thoughts of him getting what he deserves, pleases me and that scares me thinking what kind of person have I become because of his betrayal. During our breakup, he made everything as difficult as possible for me, and I chose to take the high road and exacted no revenge on him. I am quite proud of this, and it was hard not to try and screw him over. Now I have no desire or want to have him in my life, but I find I'm finding pleasure in what will be his demise. Or maybe, he and his mistress actually really love each other and can make it work. THe thoughts of him not receiving consequences for his actions, makes me a little angry.