Even when working on call, or doing some work from home, you can still maintain the mindset, "This is my home. I'm at home now. Work can't touch me here." I have tried to maintain that separation while working mostly from home -- by even physically removing myself from my office outside work hours -- but, over a long period of time, I can't help but feel my personal life is my work. I can never fully separate myself from where I normally work.
However, it's not fair to say that everyone will have the same experience, there are a lot of factors: work load, expected duties, office communication, and even your office layout -- I was worn down the most when I didn't have a dedicated office. Personally, I can't wait to get back to an office setting.
This is something you learn to manage. The fuzzy line is there whether or not you work from home. If you are a programmer or other IT type you probably already have the ability to do _some_ work from home and possibly have to be on-call sometimes (or all the time -- which I've done before).