At least in theory, Missouri and most other states have adopted the modern view that parents should share equally the burdens and joys of raising their children after a divorce. Studies have consistently reported more positive outcomes for children who had both parents remaining active in their lives after a divorce. That does not necessarily mean that the hours with the children each week should be split down the middle; instead, it refers to child custody being a shared experience with an equal commitment by both parents to the children's upbringing.
Shared custody requires a continuing partnership between the divorced former spouses. Although it is difficult for most people, the feelings of ill will or negativity toward the other parent must be subdued and replaced by a positive attitude of working together for the best interest of the children. Other obstacles may exist, such as opposing parenting styles, the tendency to use the children against the other parent, unreliable schedules, breaking promises and possessiveness over the children.
For example, shared custody requires the former spouses to personally discuss or at least to email back and forth regarding their parenting ideas and differences, with the intention and willingness to compromise where appropriate. Both parents must be able to fully control the common tendency to use the children to glean information about the other parent. This is wrong and must be rooted out by hard mental work to reform one's thought processes whenever the old patterns reappear.
Each parent must relinquish the overly possessive tendency to control every second of the children's time. The parents must trust each other and let the children be with the other parent without interference. These and related considerations do not apply, however, when one of the parents is a narcissist or has some other problematic personality disorder or significant addiction. That may require a different relationship until the erring partner is rehabilitated through professional therapy. In Missouri, a child custody order of primary physical custody to one parent with limited visitation to the other is still common; it is, however, no longer the favored way for custody courts going forward.
Source: goodmenproject.com, "5 Common Co-Parenting Conflicts And How To Resolve Them", May 25, 2018