....you no longer care about small nicks and scrapes on your paint?
....when something breaks and you think "oh that's f*cking great, just another day at the track"? (Me currently, whoo....)
....when you're thinking about your next tires two track days after you bought your current set?
....your wife complains about the ride but you think it's not stiff enough, and that compromising for her sucks?
....when you're no longer on asphalt and go "gee, what line should I try the next time" as opposed to "gee, I wonder how much my insurance premiums are going to go up as a result of this"?