Well, lots of things occur to me from that. I presume it's clear when you're available and when you're not, like any other business: if you need time for other things, then take it, don't blame your patients.
Next point is that cancelling at short notice is an entirely different matter, I agree that is a total drag. But a patient booking at the last minute is a bonus, surely? Why would you want to put obstacles in the way of somebody spending money in your business during regular hours? If you can't fit them in, then most will be reasonable about it, otherwise do you really want them in your practice?
Perhaps most importantly, scatty behaviour and unreliability is part of the person's condition. I'm not sure what field you're in, but in my view - whether we're trying to help boils, sprained ankles, or depression - disorganisation and over-pressurised lives are clues to what's stopping a person from healing, if we don't address these then we're not really healing, we're just rearranging deckchairs.
But it is also possible that something in our own condition is inviting our patients to act in a certain way. Somebody once told me we get the patients we deserve, and I believe it.
Beyond that, they're just humans, and we're in a people business, we have a choice. We must be careful what we wish for...