What habits have you picked up from living in Japan that you sometimes have to try and stop yourself doing when you go overseas because you don't think it will look right?
The comments are worth reading. There are different gestures used here, body language and different things to lubricate social interaction that go beyond simple vocabulary. If you live here for any length of time and have cultural sensitivity and a desire to adapt, you learn to do many of these. Bowing, handling someone's business card the correct way, the hand chop meaning "I need to pass through here/in front of you," the giving of obligatory souvenir snacks to coworkers after taking a trip. Three little examples of behaviors I've adopted to get along.
Some other adaptations we make seem counter-productive or flat out dumb to me, such as using Japanese nouns when speaking English to other ex-pats. Why say keitai when you mean cellphone when you're talking to another American? Others are as necessary because you're in someone else's country and you need to learn their ways. I think this is one of your important tasks when living abroad.
I'm very independent, and even in my home country I often felt like an alien observer. I had learn the niceties the hard way, with many difficulties and with much practice. Those little things, such as saying "Good morning" fifty times in five minutes because you pass fifty different people in the hallway when arriving at work. Making small talk or engaging in conversations that don't interest you in the least because you want the other person to feel validated. Using certain utensils in a certain order while dining. Drinking a single glass of wine and maintaining proper decorum at a dinner party rather than giving into social anxiety and chugging a 12-pack of beer in as little time as possible, then peeing in the bathtub because the toilet is too small a target and keeps leaping about.
Now that I live in Japan and I am a perpetual outsider, I make an effort to walk the line between my homegrown American ways and personal identity and the one I'm expected to adopt here to get along, make friends and be a productive member of Japanese society. When I go back to the US, though, I quickly revert to my original state. Maybe I don't internalize place as much as others do, or maybe there's something severely wrong with me.