I work from home too, and although I have mellowed out a bit since starting, when I first started I was really strict with myself. For precisely the reasons you say. I work in HR so had seen/helped tonnes of people to manage their time better/working relationships due to homeworking problems, so when I started homeworking I had already seen the pitfalls. I clear my desk at the end of each working day, as though I am leaving the office, so it all gets filed away, I sort out my tasks for the next day, close down the PC adn put that away also. If I am workiing in London teh next day at meetings etc, I pack teh bag up for that. Then I go out of the room and close the door. It apparently takes 20 minutes for you to switch between work mode and non-work mode. When travelling, this obvisouly takes that time up, so you get home and are out of work mode. So you shoudl try to get a routine that gets you out of work mode -e.g. collecting kids from childcare, phoning your mum or something. And in the morning when you start, get dressed (big mistake alot of people make strangely enough, although I have never felt comfortable sitting in my PJs talking to clients on the phone!), make a cup of tea while your computer is booting up, get your desk organised and revisit what you need to achieve that day (Outlook tasks is really worth getting used to using), and close the door of your office.
Like I said, I started off really strict on this, but now can allow myself to be a bit more flexible - putting the washing into machine, hang it out etc. But if I feel myself getting lazy,I either revisit my priorities for hte day (can I do that tomorrow, realistically), or just shut the door and make myself do part of it. Usually once started it is easier to continue. In fact, often the problem is stopping. Again, you need to be strict on that, and force yourself into a routine.
Hope that helps a bit - although turned into a ramble! Feel free to email me if you want to talk further...