Greeting is the first step and a symbolic one in our relation to others. And sometimes the first step can be the most important one.

Rabbi Arye Levin of Jerusalem, the tzaddik and lover of mankind (who passed away in 1969), wrote in his ethical will to his children, to teach them the way of God:

"I was very careful to receive everyone cheerfully, until this became second nature to me. I was careful, too, to take the initiative in greeting everyone."(A Tzaddik in Our Time)

When he greeted someone, Reb Arye would take that person's hands in his own and hold them in a loving, caressing way that would be electric with holiness, sending God's energy directly into his heart. There are many other tzaddikim who have taught by their example too, how in a greeting, we should focus lovingly on the person we are with.

Yitzhak Buxbaum in Jewish Spiritual Practices