When I was younger and first in the workplace, I used to assume any time someone was acting unusually toward me, it meant they were upset with me. If it went on for a couple days, I would try to clear the air with the "Have I done something to offend/upset you?" question. Then, one day an older guy I worked with gave me some very valuable advice that I remember to this day. He told me "Don't go through life internalizing everything. It's not always about you - in fact the majority of the time, if someone is quiet, distracted etc, it's because something is going on in their life that has nothing to do with you. " He did not say any of this unkindly or in a mean way, just matter of fact and kind of reassuring. It was like a lightbulb going off. "It's not all about me - people have things going on in their lives I know nothing about."
From that point onward, if someone was acting cool or distracted, I might at most ask "Is everything ok?", but usually I just keep acting normally and eventually they resumed acting normally as well. I figure if I HAD done something to upset them, they should tell me, and if they choose not to, that was their issue.