There is this surreal experience that occurs when you suddenly realize that everyone around you has a life and you're not apart of it. Like when you walk around school or campus and don't even know someone's name. That person has a family, friends, work, and their own thoughts and emotions.
You have zero idea what is going through their head. Maybe they just got a great grade on a test. Maybe they just are having a great day! Maybe they just received news someone they love has cancer. Maybe they just hate their roommate and don't know what do. The point is you don't know. So why not be a bright spot in their day?
Don't let anyone leave your presences feeling like you were a negative moment in their day. It might be the only moment you get with them. Make it a good one.