Something I've seen several times recently: person A wants person B to do something or otherwise behave differently, and gets progressively unhappier as person B doesn't do it. Person A then considers whether the appropriate response is to continue bottling up his or her unhappiness, to come out with some sort of passive-aggressive snark, or to make a scene about it. Meanwhile, person B has no idea that person A wants him or her to do that.
In fact, I've done this myself recently; and if any of you reading this haven't, I salute you, because it's a very easy trap to fall into. But still: if there's something you want somebody else to do, try asking for that person to do it before you fall too far into a funk? It won't always work; but sometimes it does, sometimes it doesn't work as intended but leads somewhere surprising and (on the balance) good, and when it fails you're almost never any worse off. And it can lead to a remarkable reduction of internal tension.
I'm better at asking in those situations than I used to be; I think I probably have Gerald Weinberg to credit for a fair amount of that? (Perhaps Delany, too.) Though, thinking more when writing this, GTD has also made a big difference, because it asks you to be clear about what you want to have happen, and whether or not you're waiting on somebody else for that to happen.