Fewer and fewer jobs have clear signals about when work is done for the day. For most of us, the work never really ends. For that reason I think it's really important to create some kind of routine that signals to yourself that the end of your day has happened and you can transition into non-work mode. Some ideas for inclusion in this routine include:

Spend a few minutes planning for tomorrow.
Clear off your desk and put all work materials away.
Spend a few minutes writing in your journal about the day.
Turn off your computer.
Do something to help you transition from work mentality to home mentality (read something unrelated to work, play a short video game, listen to some music, etc.)

The details don't matter as long as it helps you feel like you're making a transition from one part of your day (productive/work) to another part (not work/relaxing/home).

Photo by Nir.