When you are frustrated with the person you are making love too
I'm frustrated with you. But I wanna fuck. So I'm frustrate fucking you later tonight.
"Fucking Frustrating" applies to a wide range of situations, topics, and things in general not because it's a general term, but because most things in the world are, from one angle or another, extremely fucking frustrating. Typically, things that are "fucking frustrating" initially elicit a calm reaction, which quickly escalates info acute frustration through jaw clenching, then fist bawling, then screaming of the word "fuck." This gradual transition into the terminal stage is a result of the human mind's inbuilt hyperbole aversion mechanisms being slowly overcome by reality.
"Spinning rainbow ball? Fuck. That shit is fucking frustrating."