Let’s go back to your office desk. Say for example, every time you sat down in front of it, instead of doing your work, you checked e-mail, clicked on Twitter links and played Facebook games. Even if you have the most powerful processor, work-ready desk, and posture-supporting task chair, these items will absorb your behaviors and over time, their habit fields will shift in an unproductive direction.
I've noticed this with myself many times. It's one of the main reasons why I want an iPad despite its now sub-par screen: It would allow me to separate the habit field of work from the habit field of leisure more easily.
Picking up the the laptop and moving to the couch works too, though.