Book excerpt: Gratitude and happiness go hand-in-hand -- and The Thank-You Project provides an easy-to-follow approach for creating more of both. Who helped you become the person you are today? As Nancy Davis Kho approached a milestone birthday, she decided to answer that question by sending 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 a couple of former friends and exes. While her recipients always seemed genuinely pleased to read the letters, what Nancy never expected was the profound and positive effect the process would have on her. As it turns out, emerging research proves that actively appreciating the formative people in your life, past and present, can lead to a lasting increase in your happiness levels--and The Thank-you Project offers a charming, entertaining roadmap to see, say and savor your way there.