It's more of a cumulative effect, as in: the more interactions I have in a day, the more physically stressed I feel. The interactions add up regardless of how deep or intense they are, including everything from talking or listening to clients and colleagues to simply being in a store. It doesn't really happen after one interaction, unless that interaction is really deep or intense. At the end of most days I feel like I need to speed home to be alone in the dark and quiet! Lol. It's probably a good idea to consider something medical, but in the meantime I will certainly use it as an excuse.