When I'm sleepy!

Seriously, though, I generally avoid lying, but when I do it, it's usually to get out of accepting an invitation from someone to do something - someone meaning a person I don't genuinely want to spend time with - something meaning an activity I don't genuinely want to take part in. As in, "Thanks for the invite person X, but I have a prior engagement." I am actually going to be at home. No tea, no shade.