Technically I work from home, but I do have an office on a school campus as well. That is where I will meet up with my students. Many ed. therapists will have the students come to them at their home. I don't.
Anyway, if I don't go in for the therapy session, it doesn't get done. I just let them know ahead of time if I will be away for any reason. I don't have anyone else to fill in.
We own our business, we can't ever be away from home on the day I need to do payroll. Other than that everything else can be handled by phone. Our employees are great and would only call us if it was absolutely necessary.
I sometimes bring work on vacation, but mainly I try to leave it behind or it doesn't seem like a true break. If I have a writing deadline, I try to get as much done beforehand as I can so it's not weighing on my mind while I'm on vacation. It's not the kind of work that you can have someone fill in for, so I either work more beforehand or when I get back.