I absolutely concur with this Julius. I practice it all the time. On my daily walks almost all people I smile at,or wish a G'day, return a smile or greeting.

But also think about it for yourself. If you are about to be grumpy at home, stop momentarily and change both your rhetoric and tone. That means everyone around feels safe, but best of all, you will be happier. It work aaaaalllll the time.

G'day!