Co-parents can thrive if they communicate their needs and are honest with one another, otherwise, there will be a lot of conflicts. This is especially true if one person puts their wants above those of the other individual, without trying to understand their side.
This is what happened with one man whose ex-wife asked him to do a custody swap on her affair partner’s birthday so that their kids could celebrate his special day. She didn’t seem to understand how hurtful such a request would be to him and was shocked when he refused.
More info: Reddit