A life without struggle and challenge, a life free from hardship and difficulty, might seem pleasant and easy; but just as a child who is never exposed to the outside air grows up to be weak and frail, a life, a spirit, that is never tested or tempered cannot attain true happiness. Happiness can exist only in the heart of a person with a strong, solid self that is able to confidently overcome anything.

From The Wisdom for Creating Happiness and Peace, part 2, revised edition, p. 126