Smiling

The power of a smile is amazing. It turns a relatively bad day into a nice one, briefly or maybe for a longer period of time. When I drive pass toll booths or pay for my purchases at cashier counters, I find that if I smile and say "Thank you" (yes, even when I think I'm paying their salaries indirectly and therefore they should serve us :P), I get a positive response and the nicest smile. And it makes my mood better.

So, do pass on your smile. :)