There are likely hard feelings between you and your ex-spouse. However, no matter how contentious the relationship is between you and your ex-spouse if you have children with him or her you will need to come up with a solid communication plan.
Particularly if the relationship between you and your ex is extremely bad, trying to communicate with him or her about the kids might seem like a punishment. According to Divorcemag, reimagining your ex as a co-worker and limiting communications to written form can help establish a functional joint custody situation.
No longer an ex, but a co-parent
No matter where you work, it is likely that you have a couple of co-workers that manage to get under your skin. However, it is also unlikely that your co-workers have the same amount of emotional leverage over you as compared to your ex.
Usually, the first step of change begins with you. Your ex is no longer your spouse but is now your co-parent. The focus is no longer on your relationship, but now solely on your kids. Framing it this way can help you start to interact with your co-parent differently.
In particularly contentious situations, You may wish to restrict communication with your co-parent to email. Email is a more professional communication format, which may help you and your co-parent communicate more professionally. In addition, if your co-parent writes something that upsets you, you will have time to cool off. You do not need to respond immediately with an email.
Successful co-parenting requires putting enough distance between you and your co-parent to let the wrongs of the past fade into the background. In turn, this will allow you both to focus on the kids.