Great advice GoingPrimal!
I would also consider walking around with the thought that we are all connected, and through your smile, your soul wants to reach out to that other being. In our society today we are so pent up on thinking "what will the other person think, or what is the other person's intention, etc?" I know as a woman I had a hard time with that myself, especially if a male smiled at me, many times I would not return the smile, mostly out of being too conscious of the other person's motives, not out of not being nice. However today that is very different, I realized something myself, which I am still working on myself too and that is we do need to let go more and connect with others out there, even if it is through only a smile