Great answers so far.
-Your girlfriend knows the exact meaning of "the look" (which she often sees come from your face when traveling abroad) and she immediately says "you want to stop and record this don't you." You try to convince her that it is great for the soul to stop, sit quietly, and meditate on the sounds around you every once and awhile, while you whip out your pocket recorder and set levels. You record an ambience for five minutes and realize that if you go much longer, your relationship will be at risk.
-You feel shame if you use a sound from the Hollywood Edge PE or Sound Ideas 6000 in your design.
-When cooking, you go to pull a pair of thongs tongs out of the kitchen gadget drawer. Instead of removing the near-burning food from the pan, you hold them up to your ears and imagine how you'd use them as a foley prop (as dinner gets ruined).
-You've used more condoms for SM57 hydrophone experiments than their intended use.
-You believe that it is important to record traffic in every city you visit. Because you honestly think that traffic in San Diego sounds different than traffic in Portland, and you want to tell the director that their ambiences are "completely authentic."