Susan David opens by distinguishing emotional rigidity — getting stuck in fixed patterns of avoiding, suppressing, or being consumed by difficult emotions — from the difficult emotions themselves, arguing this rigidity, not the emotions, is what actually undermines wellbeing.

Why this distinction matters:

• Many people assume difficult emotions themselves are the problem to be eliminated, when David's research suggests the rigid, stuck relationship to these emotions is actually more damaging
• Emotional agility — the capacity to experience difficult emotions without becoming rigidly stuck in avoidance or reactive patterns — is presented as the genuinely healthy alternative
• This reframe shifts the goal from eliminating difficult emotions (often impossible) toward developing a more flexible, workable relationship with them

This opening establishes the book's central concept, distinguishing its approach from either emotion-suppression or unregulated emotional expression.