I feel you on this one, I edit all day every day, cutting on my own time is agonizing.
A couple things I find help:
Use a sand timer, just make yourself click shit until the time is up, no internet, no itunes. Most of the time I'll look back at the timer and it's been done for who knows how long.
Get a nonengaging tv show going in the background, you'll get bored then make yourself wander to editing.
The Devil's lettuce can get you in the zone.
Also if you're getting paid think about the money, or your bills.