Why do the ugly side shows up in Men when they are no longer with the Woman?

I can surely say that i have been through a lot with my children father, but the ugly side of him showed up in the mist of our marriage. I had to get on housing assistance because he refused to help with the children after i was a housewife for 9 years. He refused to help with child support so i had to go back to school so i would be able to get a job that pays well after i graduate. Tell me why do they act like this. I certainly wouldn't do anything to harm my kids way of living. I feel like sometimes they don't think,and they are just out for themselves at times like that. I can say that i didn't give up and i did what i thought was best for my children. Going back to school was the best thing that i could do. It is hard to find scholarships to help, so when i came across this i said why not. i am not the type of person that is picky. I am just doing what i think is right for myself and children. I hope that you respond to my Blog and tell me what you think about my situation. I would loe to hear everyone's opinion.