When working in a physical location, often times your day ends with you closing up shop, getting in your car, putting some music on and driving home. When working from home, it can be difficult to form an 'end of day' routine because... well, you're already home.
Create a habit that signals it's time to shut down. Shutting down your computer, going for a run, taking a walk, doing yoga, playing a video game - create a habit you can do most days that you can look forward to that signals your work day is over.