I guess it's still because I'm young, but if I find something interesting about a stranger or a stranger starts talking to me, I'll smile back and try to reply in a polite way, but one of my friends told me that I seem too nice when talking to people I don't even know, but I mean I'm just being myself. I don't think there's anything wrong with me, and my life is relatively calm considering I'm in high school, but yeah.
NOTE: I will almost NEVER talk to people in my own grade that I don't know, I'll talk to underclassmen and upperclassmen, but I just get really intimidated by the people in my own classes until they come and talk to me, but when I start to talk around then I get really...erm...let's say "outgoing" and people sort of start to come to me just cuz I have that type of personality I guess.