Whether it be relevant to you or not, (it should be) it seems that the more people that you brighten their days up, the more people will brighten your own day up.

It's almost like a quantity exponent, you brighten up 5 peoples days, they get put in a better mood and thus brighten up lets say 5 more peoples days, then the process repeats and this "brightness" increases in circulation and then it cycles back to you which leaves it up to you again to brighten up more peoples days whom would then brighten up even more peoples days.

So theoretically the whole world could have a good day if everyone could find it in their hearts to brighten up people who seem down.