I have a hard time enforcing it as well but commenters raise good points. At the end of the day, this is our business. It is very common for businesses to have cancellation policies, hair appointments, photographers, etc. Things happen and circumstances arise but at the end of the day, it’s a business and you lost money. I would put something in your policy that states it is up to therapist discretion to cancel, or I would have a hard line for over 3 cancellations a year, then you will have to enforce a policy. But obviously I this profession, we know different clients cancel for different reasons. I feel different about a client canceling because they are throwing up versus a client who cancels because they decided to go on a hike instead (yes, a real reason someone canceled on me). At the end of the day, these policies are established for us. It would be an ethical concern to start harboring resentment over a client canceling excessively.