One of the most effective things you can do is become a virtual smoker. Smokers get an urge and step out for a cigarette every hour - or every time they get stuck.
I don't smoke (never have) but I am trying to emulate that; the most effective way to solve a problem is to step out and do nothing for about 5 minutes. Take a walk. Look at the trees. Anything. Then when I come back I have either solved the problem or decided to leave it with a hacked together patch and work on something else; Ill probably still resolve the hack sometime later.
The opposite is to seek out some distraction, click around on facebook or HN or something - you solve nothing but spend lots of time....
I do this by going to the water cooler for a refill. I use a small cup, so I go every hour or so. I usually take the slow way there, and think about my work on the way.
Before I started working from home I would sometimes get up and pace. Fortunately we had an empty part of the building where I didn't disturb people. I felt a little self-conscious about it at first, but being eccentric is sort of fun. :-)
Absolutely. I have been working remotely for many years, with a brief stop in a couple of offices 2-3 years back. I've found that a break of a day or a few can do wonders. Don't push yourself too hard, it's not efficient. Being critical of your output without going overboard and in to the stress-zone is a hard balance to find, but gets easier over time. Another thing: when I was younger I could push myself on financial grounds; now when I lack the spark for implementation I instead push myself on integrity grounds. Not sure if anyone else has this experience? I for one still really enjoy my work.
Of course, the problem wasn't really abandoned -- I was thinking about how to solve it the whole time. But I wasn't writing any code.
Forcing yourself to write isn't necessarily best.