Make a promise to yourself right from the start not to bad mouth your ex husband in front of your children. (That includes phone calls, which I have been guilty of.) Experts say that it is not the divorce that harms a child, it is the aftermath. When mom and dad continue their battle after the divorce the children suffer greatly.
If you have spoken harshly about your child's parent within their listening range, take ownership for your mistake. Simply apologize to your child in an age appropriate way.
If you learn that you are being bad mouthed, take the high road. The view is always better there. Refrain from blasting back and don't show any personal emotion, especially if your child is telling you. Stay calm, focusing only on your child's feelings. When you realize how painful it is for them to hear harsh words about you, the high road will become the only road.
Blessings,
Virginia