When you're in a joyful mood and turn up all excited to meet someone and notice that they only dragged themselves there half-heartedly and show a lack of enthusiasm in their expressions, that dampens your spirit a little.

The urban slang for this is buzzkill.

We are easily prone to having our own emotions affected by those that we interact with, even if they're just a stranger on the street. 

When we turn that around though, we notice that we have a similar effect on everyone that we interact with during our day. 

This is a limitless inflow of opportunities that we have day after day to entice a positive outlook in those that we interact with everyday. 

Radiate joy and possibility. 

Don't be a buzzkill.