Away, as at home, I have a default greeting: howzitgoin.
Away, as at home, the mental wheels slip a little when the default doesn't match with the situation in reality.
Here in Italy, buon giorno—"good day"—works for just about every hello from good morning until some fuzzy part of the late afternoon. So I get in the habit of buon giorno-ing everyone. Buon giorno. Buon giorno. Ciao. Arrivederci. &c.
In the evening it's a little different: buona sera—"good evening". It's not difficult to hear or say. But in that moment when the taxi driver or the waitress says buona sera there is a little bit of scrambling internally to hear something different than buon giorno and say something different than buon giorno in return. I have been in Italy for eight days of my entire life, so the rut isn't that deep, but the rut is comfortable and easy and takes some energy to leave nonetheless.