(no subject)
Dear person who's just asked me to help out with a children's class on Sunday:
The point of asking in a case like this would be to genuinely inquire if I was available, and if I weren't to be in a position to make adjustments accordingly. Asking me after I've already been aware of the fact that you unconciously volunteered me and would be foul-mooded for the rest of the day (at the very least) if I declined turns your request into a mere formality.
I'm sorry that you're so anxious about this. Sunday will go splendidly, I promise.
Love,
--Zalein