A warm, friendly, excepting smile can go a long way and is also part of the healing process. A smile is generally an expression of positive emotions, which can uplift a soul, who in turn passes that energy to another.

It is also about body language. It is a means of understanding something unspoken which can be as simple as, a friendly greeting.

The frequency of a smile received can vary and quickly move into your intuitive side the right brain. What does that smile mean? Okay, I got it! Now you react to the smile perhaps returning it with a smile. Laughter is a related healing tool and is also contagious as it is a high frequency emotion.

Researchers measure the value of a smile   PhysOrg - May 10, 2011
Researchers at Bangor University have placed an economic value on a smile, demonstrating scientifically the effect that a genuine smile can have on our decision-making. The psychologists call this social information and say that it has more of an effect than you may imagine.