Have you ever noticed that no one is particularly fond of the resident sour puss? People who constantly complain, are rude or simply lack the social skills necessary for workplace interaction are a chore to be around.
This doesn't mean that we must turn into the office clown and yuck things up to be successful, but we should be cognizant of our demeanor at work. Take a look at Anita Bruzzese's article Why Laughter May be Critical to Career Success to see how laughter may benefit you at work.
Take a moment to exercise your funny bone.