I only have one person that I will see if I am in a bad mood and ONLY because if I see him I know I will end up in a great mood.
But my threshold for a bad mood is pretty high. If my day is so shitty I am in tears (not a normal occurrence by any means) I will cancel and reschedule and try to make it up in some way. But if I wake up cranky and feeling like.........."god if I have to see one more dick today" that is passing. Any time I have stood in the shower and felt like I really wanted to cancel because I just didn't care ended up being one of the best appointments ever.