I am almost always in the mood, however if it' a matter of attitude - I switch that off or don't take any appts that day at all.
I do agree that I have numerous regulars, even when travelling, and I do count them as friends. And knowing that I have a friend coming does alot to cheer me up. Plus if it is a good session, both of us should be smiling afterwards.
I had one time where someone showed up for appt within minutes of me getting some bad news, I broke down crying. He was a regular, so we talked first and by the time he left, things were much better.