You know you're obsessed with Valve games when you see goombas and shout "GAH! forget! HEADCRABS!"
You know you're obsessed with Valve games when you look at the back of people's heads and ask "Where's the valve?"
You know you're obsessed with Valve games when you buy one of those headcrab hats
You know you're obsessed with Valve games whenever someone hits you in the back with anything and you shout "SPY!"