Authoritarian parenting, as in "my way or the highway," and its opposite, permissive parenting with lack of limit setting, may be linked with difficulty with emotional regulation in children. In contrast, an "authoritative" parenting style is associated with an enhanced capacity for emotional regulation, flexible thinking and social competence. An authoritative parenting stance encompasses respect for and curiosity about a child, together with containment of intense feelings and limits on behavior.
Parental authority is something that in ideal circumstances comes naturally with the job. It is not something that needs to be learned in books from "experts." In fact our culture of "advice" and "parent training" may unintentionally undermine that natural authority.
But what might cause a parent to lose that natural authority? Stress is far and away the most common culprit. That stress might be in part coming from the child himself, if, for example, he is a particularly "fussy" or "dysregulated" baby. It might come from the everyday challenges of managing a family and work in today's fast-paced culture, often without the support of extended family. It may come from more complex relational issues between parents, between siblings, between generations.