It depends on what you mean by skipping, as others have said. If you cancel ahead of time, it may or may not be acting out, depending on your reasons for canceling. If you are trying to provoke a certain response from the therapist or trying to be punitive, I see it as acting out. If you just don't attend the appointment, in effect "ghosting" the therapist, I definitely think that's acting out. If the therapist is so unwilling to listen or take your concerns seriously that you actually have to resort to not attending therapy, instead of just talking about wanting not to attend, something isn't right and you need to start questioning if you need a new therapist. I have threatened the therapist before that I will not come back, and she has responded appropriately. Granted, I think threatening to not come to an appointment is also acting out, but at least there's a chance for dialogue with that option - and resolution without the wasted time of skipping or ghosting a session.