... is what we think of as our territory (psychologically), like a halo of comfort around us. Altough it's difficult to actually measure it as it differs from one person to another, we can always sense when we invade someone's personal space. If you care about others and just watch closely you will notice reactions that may hide discomfort, anxiety or even anger: sudden scratching, rapid blinking, focusing eyesight on a distant place, sighing, explicitly stepping back and more.
Today's story is about a young girl who's pregnant. She got over the point of tired and became angry at people always petting her belly. In this obvious case of invading personal space I think it's very good that she chose to protect herself by telling it with a t-shirt. There are always solutions to avoid these unpleasant feelings: for starters we can get used to asking before stepping in someone's personal surrounding and touch them. We can also pay attention to one's body language to understand if they want intimacy or distance.
Even kittens don't let you pet them when they are not in the mood. :-)