Happiness for the individual alone is impossible, and peace in terms of the environment alone is impossible. There can be no happiness exclusively for the self, nor unhappiness exclusively for others. The happier we make others, the happier we are, and as long as a single miserable person exists, our own happiness cannot be complete. This is the meaning of the true aspect of all phenomena. Hence, the heart of this teaching is a neverending effort to transform reality.

From The Wisdom for Creating Happiness and Peace, part 2, revised edition, p. 17