Feel like, at the risk of sounding dramatic, I've awoken out of a fever. Should've gone out last night, but I was, as the saying goes, not fir company for man nor beast. Words coming out turned into razor blades, and all that. But this morning, it seems to have apssed, which is for the best. And now, coffee and, hopefully, pretty waitresses.
Just because you're civil to this person doesn't mean that you're friends -- or that you want to be. Keep reminding yourself of that, especially if the other party doesn't seem to understand your boundaries.
Lately a certain person has been getting under your skin, but they don't mean to. In fact, they have no idea they're having this effect on you at all! Say something in a kind way and the issue will soon be resolved.