- Definition: People have a particular happiness level that we return to after good or bad events, a process called hedonic adaptation.
- Insight: Hedonic adaptation helps us move on from tragedy; but also means that joy from positive events doesn't stick around for long.
- Insight: Humans are so effective at adapting, we can often take things for granted.
- Insight: We can raise our base level of happiness: "happiness is hackable."
- Principles: (1) Practice gratitude; (2) practice forgiveness; (3) practice giving.