It does seem a strange thing to count suffering as joy, yet there's a truth here in that suffering helps to build one's character. Some of the most beautiful people I know are those who have passed through the flames and come out strengthened. If it happens to clay, why shouldn't it happen to us.
Change is a fundamental element of consciousness. It is what calls our attention, awakens it, stimulates our questions. We see the red coat in contrast to the white snow... Without change, our minds become dull and unaware.