In her bestselling book The Happiness Project, Gretchen Rubin discovers the pleasure of writing just one sentence every day. The Happiness Project One-Sentence Journal helps you to make a fascinating and revealing time capsule of the next five years of your life. Simply turn to today's date, reflect on the quote at the top of the page, and jot down just one sentence (perhaps about something good that happened that day).

This daily ritual is highly do-able and provides a striking sense of accomplishment, and as the years...