I'll tell them I'm tired, which isn't a lie.
I'll say, "It's fine. I'm just in a quiet mood today. It's been a bad week. For sleep, I mean. For sleep, of course, because that's all that's wrong."
And they'll believe me, and it'll be fine, and I'll just not care and everyone will forget about it in a few seconds and won't care and won't care and won't care.