...you're tempted to stop and examine every bike you see, no matter how nice or "crappy." Your walking companions are accustomed to this and stop in front of bicycles pre-emptively when you are with them.
... you walk by a freshly painted house or fence and wonder what the closest matching RAL colour code would be. You narrow it down to two, both of which you remember by heart.
...you get confused when trying to walk places. You are accustomed to the cycling route.
...you happen upon a scenic spot, and you wonder how well your bike would photograph there.
...it is impossible to snap a photo inside your apartment without getting at least a small piece of bike in the frame.
...you decide to rent a boat on vacation, and it ends up being a pedal boat.
...you arrive in a foreign country and the first thing you do is sort out your bike situation. Later you also tend to the small stuff, like making sure your mobile phone works and that you can withdraw cash. You don't even bother with public transport.
Bicycle in Vienna? Check! Despite the pouring rain and the worst jetlag ever.