One Religious Practice with Devastating Spiritual Consequences

There are certain culturally supported beliefs that are widespread throughout the modern institutional church. It doesn't matter what the particular flavor of the church is, its denominational affiliation, or its position on the charismatic/conservative spectrum. Regardless of these differences, almost every congregation holds these beliefs and adheres to these practices. Not only are these practices pervasive, they're also so deeply held that virtually no one questions them.  The problem is that they have devastating spiritual consequences.