When you sleep, you either dream of amazing places to hide new caches, or you have nightmares of that DNF earlier in the day.
When the trunk of your car is packed full of plastic baggies, tupperware, a big stick, flashlights, lots of AA batteries, geocaching clothes/shoes, and bags of swag.
When your family and friends get irritated with you because anytime you are ever near a geocache you know about, you tell them the size/difficulty/terrian/hint/last 5 logs of that cache and blab about how it's on your "to-do" list.