Sonja Lyubomirsky: Surrounding yourself with people who are happy is going to make you happier. Conversely, if you're married to a negative person, it's going to take a toll on you. The problem is that we adapt: We really have to work to appreciate what we have.
Ed Diener: It's certainly true that if you're around somebody that's giving you many compliments, you start giving people compliments yourself. If you're around people who are more positive in general, you get more positive. On the other hand, when you're unhappy and you're bitching all the time, you're not just affecting yourself, you're affecting other people, too, and you're also teaching them about how to act or not act.