I second that emotion. It comes back to you eventually; it always has for me.

My wife and I pedal around the neighborhood quite a bit: she has a loud, two-tone bell which she rings whenever she sees anyone. Maybe half of them respond and wave back, but the other half tend to be real sour-pusses. I try to be optimistic and think that it's worth ALL the effort to be friendly and helpful even if it only pays off once. (Or is that just my holier-than-thou righteousness chattering away??)