The author and narrator who presents herself as a relatable figure struggling with anxiety, control, and micromanagement. She uses her own life experiences as the primary case study, detailing her journey from a high-stress "control freak" to someone who finds peace by allowing others to be themselves.

Mel's daughter and the catalyst for the book's core concept. She acts as the voice of reason during a chaotic pre-prom party, delivering the instruction to "Let Them" which becomes the foundational mantra of the theory.

Mel's son, whose unstructured plans for his senior prom serve as the opening anecdote of the book. His relaxed attitude toward logistics contrasts sharply with his mother's stress, illustrating the friction caused by trying to manage another person's experience.

Mel's husband of over 25 years, frequently appearing in anecdotes regarding marriage dynamics and emotional regulation. He is depicted as a steady presence whom Mel learns to stop trying to change or manage through the application of her theory.

A Harvard physician and expert on stress who provides the scientific backing for why the brain craves control. She serves as an authoritative figure explaining the physiological differences between the "thinking brain" and the "survival brain."

A psychiatrist and expert on emotional regulation who explains why adults often react with childlike emotional outbursts. His insights help the reader understand the futility of trying to force motivation or change upon others.

A renowned relationship expert who contributes a framework for dating and commitment within the book. He appears in later chapters to teach readers how to apply the theory to romantic relationships and stop chasing uninterested partners.