How do you deal with somebody who doesn't know you're angry at him/her?
I don't know... It's awkward to make clean breaks when you're gonna see other around for a long while.
But I reached a conclusion... that is to treat people how they treat you. If they're insensitive and selfish around you, you gotta be the same to them. No emotional investment.
But of course to people you genuinely love, lay the love on them thick. Yay.