Having gratitude and appreciation for the countless people and things that support our lives—that awareness, that feeling, that joy—will invite even greater happiness. Rather than being thankful because we are happy, being thankful itself will make us happy. Also, chanting with gratitude puts us in rhythm with the universe, turning our lives in a positive direction.
From The Wisdom for Creating Happiness and Peace, part 2, revised edition, pp. 66-67

Daisaku Ikeda

Because of the principle that earthly desires lead to enlightenment, suffering becomes enlightenment and happiness. The greater our problem or sorrow, the greater the happiness we can change it into. This is the power of daimoku. That’s why those who chant Nam-myoho-renge-kyo do not fear anything. There is no need to. From The Wisdom for Creating Happiness and Peace, part 2, revised edition, p. 49

Daisaku Ikeda

No matter how fun-filled or entertaining your life may seem, without a sense of fulfillment, it cannot truly be called happy. A life without any real purpose, which leaves you feeling only empty, is an unhappy one. It’s also important that we choose self-improvement over pleasure. Those committed to self-improvement have depth. They are attractive. They have hope.
From The Wisdom for Creating Happiness and Peace, part 2, revised edition, p. 212

Daisaku Ikeda