Separate as much as you can. A commenter suggested dual booting. Putting your work environment in a virtual machine might be another option.
On my laptop, I keep separate browser instances for work and play:
google-chrome --user-data-dir=/home/workuser/.config/google-chrome-workuser
google-chrome --user-data-dir=/home/playuser/.config/google-chrome-playuser
Some people are able to switch contexts easily. If you're one of these people, advice given here may not apply to you. If you do find yourself having trouble keeping yourself focused at work, try doing things to keep your environments separated. It doesn't have to mean physically lugging your tower PC to a different room (but don't rule it out). Try creating different user logins, or at least different backgrounds and color schemes.