You are hurting you child if you are doing any of the following:

Subtly or directly putting the other parent down.
Ex: “Mommy/Daddy said you will get fat if you eat too much sugar but she/he doesn’t  know how to be healthy.

Having a negative attitude toward the other parent during the exchange.
Children pick up on body language and tone of voice and especially actions like slamming doors or walking off in a huff.

Not letting your child talk to the other parent when her she is with you.
Young children especially need reassurance that the other parent still remembers and cares about them. The contact needs to be age appropriate. For younger children “FaceTime” on the iphone is good because they can actually see you. Teens would much rather text, I’m sure. Empathize with your child and listen carefully to what they need.

Continuing to go back to court.  
The research is very clear that the conflict, including court battles, is the damaging factor to children of divorce, not the divorce itself.