Having divorced means that both you and your ex have your own lives again, that you are not trapped in a vicious cycle of fighting and pain anymore.
This new found freedom should be translated into making your kids happy. Concentrate on them and their needs, if you have to stay in contact because of the kids, be civil and kind to one another. Don't be getting into petty fights over the kids, in front of the kids. They've probably have enough of that when you guys were in the process of getting divorce. So when the kids are around, be kind and be friendly.