Wary People

People are always wary of other people. That's because you never know who you're going to meet. There are billions of People in this world so the kind of Person you'll meet next is always a mystery. Whether they'll affect your life in a positive or negative manner is completely up to their actions and your perspective. So, as a species, we have a habit of always being on the look out for the unknown because we realize our best defense is simply being aware. Being aware of the fact that anything COULD happen is the best way to prepare your self for anything TO happen. Once you acknowledge something as "Unknown" you acknowledge that the possibilities  as to what it could be are virtually limitless. That's why every time someone walks into a room full of people everyone looks up to see who it is. It's like they're all trying to be aware of a new presence that has the potential to affect their entire experience.