A smile is not only the result of happiness but can also be the cause of happiness.
SGI President Ikeda says:
Buddhism teaches that whatever our individual circumstances, we can always discover the capacity to help others; it also assures us that those who have suffered the most have the right to the greatest happiness.
By helping other people become happy, we too become happy. How can those suffering in the depths of hell, who have lost the will to live, get back on their feet? Merely thinking about our own problems often causes us to fall even deeper into despair. But, by offering a hand to someone who is also suffering, we ourselves regain the will to live. Taking action out of concern for others enables us to heal our own lives.