Treat home office as the name says - as office. With 1 little benefit. That means get out of bed on time, shower, have breakfast, do push-ups. Whatever your normal morning routine would entail, do it. Get properly dressed.
When turning on your computer, pretend you're in your office. Don't watch TV or start vacuuming. Stay focused on your task, do your work until you're done.
The 1 little benefit: If you're really efficient and get everything done a little quicker than you would in the office, maybe because of less water cooler chat or less people distracting you, reward yourself and knock off a little early, if you can. After all, it's about getting the job done, and not about sitting x hours in front of a screen.