Regular Backups is the way forward I would say. I am a MAC user, but there are plenty solutions for Windows users as well.
When you are away from your computer, lock the screen, or put it to sleep. In Windows you can use [Windows logo key] + [L]. For Mac users, firstly you need to set up a password in the Security area in System Preferences, then to put screen to sleep press [CTRL] + [Shift] + [Eject].