What is the main idea of you Have No 'Right to Happiness' by C. S. Lewis?

The basic thrust of this essay is that humans have no right to expect that life will make them happy, and especially that there is no "right to happiness" that permits you to break moral codes to make yourself happy. One example that he uses is a married couple where one of them, say the wife, becomes mentally ill. Should the husband be permitted to "dump" her or have an affair while she is ill because he has "a right to happiness"? The answer given by Lewis is definitely No. Happiness is a gift, not a right.