After the visit to the knee surgeon, I visited a physical therapist for the first time ever. As a freelance writer, I charge an hourly rate, and that rate wasn’t significantly different from my physical therapist’s per-visit charge.

He charges me about the same for an hour as I charge my clients, and he can afford an office in downtown San Diego, a receptionist, instruments of torture (physical therapy tools)…. AND he can afford to have good chocolate in the bowl on the desk plus bottled water for clients. Why don’t I have the good chocolate?

The answer: It’s all in the volume. I saw his appointment book. He had a new client every hour, booked solid from 9 a.m. to 6, plus a few overlapping. In comparison, yesterday was one of the toughest writing days I’ve had — I finished at about 11 p.m. But I only billed out about 6.5 hours total.

Perhaps there are writers out there who can write straight for 8 hours or more. I’m not one of them. To earn his fee, my physical therapist can set me up on a machine or get me started with an exercise and leave me for a few minutes to check on this or review that. When I’m earning my hourly rate, I can’t multitask at all. I don’t listen to music. I turn off my email. I hide my BlackBerry so I don’t see the little red light blink when more email comes in. It’s not excruciatingly hard — it’s just something I need to focus all my energy on. And it’s something I can’t do for hours and hours and hours at a time.

I guess my business model means I’ll have to stick with water from the tap and a tin of Altoids that my sister got me for Christmas.