Ahhh, the Premenstrual Syndrome. Unlike the female orgasm, this is not a myth; it's all too real. It sucks for the girl, it sucks for the guy. No one wins, and there's pretty much nothing anyone can do about it.
Here's a hypothetical conversation between a guy and his premenstrual girlfriend:
Guy: Hey, shmoopie. How was your day?
Girl: Oh, so all of a sudden you care about my day?
Guy: What do you mean? I always ask you about your day.
Girl: Yeah, but you never actually listen.
Guy: What're you talking about? I know the names of every person you work with and every female office rival you've ever had.
Girl: Of course you're going to say that.
Guy: What does that even mean? Look, what's wrong? Is there anything I can do?
Girl: Why does something have to be wrong with me? And why do guys always think they can fix everything?
Guy: Okay, then. Well, I'm just gonna go sit in the corner in silence and try not to blow my brains out. Let me know if you need anything . . .
Now, that never actually happened, but it is very typical of the no-win situations that PMS can engender. Like I said, we're powerless against it. All you can really do is hold on tightly, and wait for the storm to pass. Godspeed.