High-conflict co-parenting can be stressful to the parents and the children. While you might not be able to do much to shield yourself from the matters, you do need to do what you can to protect your children from this type of unnecessary stress.
One thing that might help you remain calmer is having a clear plan for handling contentious matters. This should be outlined in the child custody order and include expectations of respect. Including detailed steps to follow for resolution can help co-parents reach accord with as little stress as possible.
Under no circumstances should you use messengers during a conflict, including using your children to relay messages back and forth. Conflicts should be handled directly between you and your ex. In some cases, the use of a mediator can help keep the discussion on track but you and your ex still have to be the ones negotiating.
Another point to remember is that you are the only one in control of your own actions. You can't give your ex control over how you feel. Sometimes, a co-parent will use manipulation to try to get what they want. When you let this happen, you are putting someone else in control of your emotions.
When you are in this position, remember that your children are looking to you and their other parent for love and stability. The goal of any conflict resolution involving custody matters should be your children's best interests.
If the conflicts are serious and can't be satisfactorily resolved, you might need to turn to the court to rule on your parenting plan. It is possible to modify current orders as long as the changes are what is best for the kids.