SYDNEY: You don’t seem to realize that a poor person who is unhappy is in a better position than a rich person who is unhappy. Because the poor person has hope. He thinks money would help. I tell you there is no despair like the despair of the man who has everything.

Jean Kerr (1922-2003) American author and playwright [b. Bridget Jean Collins]

Poor Richard, Act 1 (1965)

This line is in both the original written version and the stage production; in the former, though, there are some additional lines in between, tying the observation back to writers and their unhappiness even when successful.