Abstract Private events can have a dominant function in human behavior, especially with regard to the experience of self and selfing behavior. This article presents the building of selfing behavior throughout the early interactions of responding to others’ behaviors and discusses the impact of learning to relate (i.e., learning human language). Special focus is on the significant impact of deictic and hierarchical framing in building self-contents, overaching abstract motivations, the abstraction of I, and the subsequent derivation of more self-contents. Also covered are the patterns of responding in coordination with one’s own behavior (psychological inflexibility) and responding hierarchically (psychological flexibility); and hierarchical responding as the final common pathway for the many faces of therapeutic processes towards building psychological flexibility. Finally, the experimental evidence that has been signaling this path for years is summarized.