How should I respond when people disparage their work?

Often, people often make comments about the great burden that work is -- not in the sense that they're unhappy with their current job, but that they resent the need to work at all. These are the kinds of people who live for weekends and vacations. I don't feel that way about my work, and I think these people are missing so much in life. How can I respond to such casual remarks in a way that might make the person re-think their attitude?