It's not good to act "too familiar." That's not what you intend, I realize. But, if you keep getting this consistent feedback, then you have to learn from it and accept that how you are coming across is not what you intend and you need to make a change.

When you are around strangers, keep this in mind. You don't know those whom you don't know. There are all kinds of weirdos and creeps and every kind of criminal walking in the world around you. Stop trying to feel all warm and fuzzy toward strangers indiscriminately. You don't know what they are about. Some of these people are possibly even a little afraid for your sake because this smiling at strangers could get you noticed by some very bad person.