The #100HappyDays challenge—Can you be happy for 100 days in a row?—is a viral online movement that has had more than 8 million participants since its launch in 2013. Those who have completed the challenge have found that spending 100 days intentionally finding or creating a happy moment each day—whether through trying something new or just seeing their daily life in a new way—added up to long-lasting feelings of optimism, gratitude, and satisfaction that far exceeded the sums of their parts.

This daily guide will help readers find happiness in their everyday lives and complete the #100HappyDays challenge. The 100 directives, big and small, will inspire the reader to take action (“Compliment a stranger,” “Hike to a scenic spot,” “Be the first to apologize”), with text explaining both why the action contributes to happiness and how best to implement it. Sprinkled throughout are essays that delve into the science of happiness on topics ranging from meditation to music therapy to physical activity.