Who helped you become the person you are today? And, have you ever thanked them? Approaching a milestone birthday, Kho decided to send thank-you letters to the many people who had influenced her, helped her, and inspired her over the years: family, friends, mentors, teachers, co-workers, even exes. Her recipients always seemed genuinely pleased to read the letters, but Kho never expected the profound and positive effect the process would have on her. Here she shows how to appreciate the formative people in your life, past and present-- and perhaps create a lasting increase in your happiness levels.