Yea, what Restraint said, I think I have a pretty heavy guard up. But my moods differ too. Some days I say "Oh get over it!" and some days I feel everything.
Usually it is neither, I just see a logical explanation for their situation or I know that I don't have all the facts so I don't think too much about it.
Of course, it depends on the scope too.
If someone broke up in a short-term relationship I really don't care too much, if someone was just in a life threatening accident or lost someone through death or divorce, that is a different story.
But yea, some people understand how to tug those strings.