When you and your wife have to drive somewhere together and you tell her we have to take her car, because she doesn't have a seat in yours. "Ahem... that's not your seat. That's my pipes and tobaccos seat."
When you get a new pipe and immediately start thinking about the next one you “need”. Oh wait, that’s PAD and that is a clinical disorder.
When you realize what Zen “feels” like. You then think about the experience often.
When you know the mailman on a first name basis and you've memorized his exact weekly schedule...
When you can accurately guess the weight of an object between 25g and 45g just by the feel of it...