Dvar Torah by Reb Ari Waldman @ Mystical Paths
In Yaakov Avinu's blessing to Yehudah it says, "Your eyes will be red from (an abundance of) wine and your teeth white from (an abundance of) milk" (49, 12 according to Rashi). On this pasuk the Gemara says "Rabbi Yochanan says, "It's greater to smile at someone than giving him milk as the pasuk reads (better) the whiteness of the teeth (than) milk!"
Harav Shlomo Volbe in his Alei Shur, book 1 page 190 writes, "Even a small baby can discern a happy face or upset face! If you scowl at him, immediately he'll cry. If you light up with a smile to him, he gets excited. Who knows what promotes the child's health and development more, the food he gets or the smiles he receives?! It's clear that a child growing up without the light of smiles is exactly like a plant that grows without sunshine!! There's no way he'll grow up healthy!! On the other hand, even a small baby can give when he lights up with a smile to others! From his first smile and onward he is already higher than any animal. For this smile is really the light of his neshama shining out of his small and helpless body!! The more a child develops in a healthy manner, the more he smiles out into his surroundings creating an atmosphere of love and happiness! This is the strength of the neshama, shining out its first rays. This is its whole essence, to light up with a smiling countenance!!"
Harav Volbe continues, "These two life forces are the bedrock of any social interaction and of all society. The first, the hunger a person has for his friend's smile. Second, the power and desire to give which is embedded in the hearts of anyone who has a neshama! If you were to contemplate the way people relate to each other you would see how people can live side by side with their neighbor or friend without finding a way or language to communicate with one another. They can live with anger and bitterness because of their misunderstanding one another. If you search for the source of this, you'll find that always one person is waiting for the other to make his overtures and approach him. Only then will he respond in kind! Be it a Rebbi hoping for his student to approach him with his problems or the student waiting for his Rebbi to approach him! A community Rav who wants his flock to come consult with him on communal matters and the community may be waiting for the Rav to initiate his helping to solve those matters! In this manner people can live side by side without approaching one another!! Meanwhile the gap between them is widening into a gaping abyss which they’ll eventually be unable to bridge. Each side has his excuse why the other side should come to him! These aren’t excuses; they are just a display of foolishness! The first thing they should learn is "I must shine with a smile to my friend first!!And not ignore my friend!" How great are the words of Chazal "Be first to greet with Shalom every man!!"
"This is not such an easy task! For Two Years Harav Avrohom Grodzensky, a primary disciple of the Alter of Slabodka worked on "sever panim yafos" greeting people with a shining happy countenance!!" It was said of Harav Shlomo Zalman Auerbach that he would practice smiling in the mirror to receive people in a kind manner!! No wonder people remember him for his smile!! People sometimes come to a family simcha when they didn't feel well. Understandably, it was hard for them to smile. But looking back at a photo album, they regret they didn't at least try to smile! Don't you want to be remembered by your smile?
In summary; You have a neshama that's waiting to shine out to others. This is done by a, making the first move and b, smiling! You can fill the world with sunshine! Today!!