It doesn't matter whether a therapist is human or not. They are being paid to perform a job and if they can't do their job they should cancel the appointment, find a different job, or suck it up and do it right. If they have some sort of a yearly problem, that's easy enough to plan around. Take a week off, see their own therapist, or they can lie in bed in the dark weeping for all I care. But don't screw with clients, take their money and expect to be excused because oh no they're human