Everyone has one, it's the point where it dawns on you that you've forgot to do something, left something behind, etc..., and decide to say "screw it, I've come this far."
Mine is 3 seconds after I've moved on to the next thing, no joke. Last night I said "fuck it" three feet after leaving my car when I couldn't remember if I locked the door anymore (yea I'm like the only person in America without a clicker right now, leave me alone). I literally wasn't out of my parking spot, hadn't made it past my rear bumper, and I couldn't be bothered to go back and check. As I type this I'm just hoping my car is still in one piece. Yea it was a gamble, but I think it was worth it, if I go back then I have to start going back for everything, and frankly I like having the shortest point of no return known to man.
It applies to everything too, couple weekends ago the girlfriend and I were heading to the beach, hot as hell and sunny out, I forgot my glasses on the kitchen table. The exterior door to our building had just closed when I realized I forgot them. Couldn't be bothered, I'd have to walk up some stairs, down a hallway, then all the way back...that's like 60 seconds I'd never get back, no, I'd come to far. I went out and got a headache from squinting all day but I'd say it was worth it.