1. Get up and move
Rather than sit in front of your computer or TV all day, get up, do some stretches, jog in place, do pushups, and move until your frame of mind has changed.
2. Make yourself accountable
You can do this with people around you or even with your motivation buddy above.
A great way is to announce your change publicly and be vocal about it.
Hit the social networks, your blog, write letters, whatever it takes to make yourself more accountable to getting work done.