Open mouth, insert foot

For the most part, I do a good job of not saying the wrong thing at the wrong time. I never assume a woman is pregnant unless I see the baby poking it's head out. I typically don't make comments about people's appearance, as you never know if the haircut you like is despised by the owner of said haircut. I did make the mistake (once) of asking a female co-worker what she had done with her hair. Apparently, there is more than one way to take that comment. Recently, I screwed up on a grand scale.

One of my bad habits is to come in on a conversation and make off-handed comments without knowing the context of the conversation. Usually it results in at least a polite chuckle. Last week my two officemates (yeah, I'm tripled up. It's a bit cramped) were talking and I walked in on the conversation. I heard Doug say something about spending time with family. Being the smart-ass I am, I said "Who'd want to spend time with family?"
Doug responded, "My uncle. He died last night."
Apparently he had pancreatic cancer and instead of fighting it out in the hospital he went home to spend time with his family. Looks like I've got a bad habit I need to break.