If you suffer from ADD you may be all to well aware of the dangers of hyperfocus when you get into a project. Four hours after starting, you pull your head out of the project to find that your family will be home for dinner in 5 minutes and you were planning to shop for groceries before the end of the day. Meanwhile, the project at hand is spread across the dining room table. Sound familiar?
Consider keeping a time tamer alarm close at hand for these situations. Set the alarm for 45 minutes to an hour. When the alarm goes off, get up from where you are working, walk around, get a drink to stay hydrated. After 5 minutes or so return to the task at hand and reassess the degree of focus you have given based on your objectives for the time you have to work.
Remember to reset the alarm before you return to work.