Every time I smile, I spread positive energy into the world.

A supermarket checkout at nine in the evening is one of the least rewarded places to be standing. The person there has scanned four thousand items and been spoken to as furniture for most of them.

A smile in that setting is not decorative. It registers as being seen, which is rarer to receive at the end of a long shift than most of us assume.

The catch is that it has to be real. Everybody can tell the difference between a smile aimed at them and one performed near them, which means the work is not the face. It is looking up first.