I'm usually okay - but sometimes I am not. I get tetchy, irritable. It's probably because I'm tired.
It's usually after a particularly demanding day. There's been lots of people to talk to. Now that's all over, I just want to be left alone to recharge. It's nothing personal; I know what I need.
A half-hour might be enough. It might be longer.
Just leave me be. I will be fine.