I think it is more likely it will go fine- I have seen something in the region of 10 therapists and none of them have ever yelled at me. None of them seemed in the slightest bit likely to yell at me, even when I have forgotten my appointments.

Forgetting an appointment and not going back is really par for the course for these people. They would have to be really, really bad at their jobs to yell at you and banish you. Like so bad at what they are supposed to be doing that they likely would have been fired after a week. Their major shtick is to sit around being nonjudgmental and accepting. Yelling and banishment is really antithetical to what the whole ethos of the profession is about.