I’ve just figured out why

I’ve just figured out why I’ve been so testy over the last couple of days – reduced coffee intake. Although, of course, we only get decaf here at work. But I have my first (very large) mug of coffee for today, and I can feel my mood improving already.
In fact, I’ve been so tired and irritable all week that I haven’t even been to the pub. Must put that right tonight.