Have you ever seen someone you know in a public place, and you haven't really talked in a while, and you're not sure if you should say hello?
So you act like you don't see them, give yourself a moment to get your thoughts together. Will they be miffed that you haven't said anything to them in so long? Will trying to be friendly make it worse?
But then, to your horror, you realize that if you've seen them, then they've probably already seen you! Now they've already seen that you're not responding to their presence, and they must think that you've already snubbed them. Oh no! The whole encounter is ruined, before either party has openly acknowledged the other's existence! NOOOOOOOO! How could it all go so wrong?!?!
So yeah. Has that ever happened to you?