From Improving the World (#792) by Rabbi Avigdor Miller
One of the big achievements we have to learn in this world is we have to make other people’s lives sweet, you have to make people’s lives happy. That’s one of the tikkunim (reparations) that make this world a better place because of your being here.
It’s an art that you have to study, you must master how to treat people in order to make a tikkun wherever you go. Instead of being a weed, a thorn, you have to be a flower in this world, with beautiful color and fragrance so passersby look and have pleasure from you.
Instead of being a weed, a thorn, you have to be a flower
“Hevei m'kabel es kol ha’adam b'seiver panim yafos — You should greet every man with a pleasant countenance.” (Avos)
As you pass people on the street, don’t pass them by with your head down, with a look from the corner of your eye. Make it your business to raise your face and shine your countenance upon them; like “Ya’er Hashem panav eilecha — Let Your countenance shine upon them” (Birchas Cohanim).
The Tomer Devorah says just like Hashem makes His countenance shine, your countenance should shine on people. Make it a principle, “Ya’er” your face should shine on people. And the gemara says, “hamalbin shinayim luchaveiroi — if you show your white teeth to your fellow man,” you smile to your fellow man, “tov mimashkeihu chalav — it’s better than giving him a drink of milk.”
In Slabodka, the Alter said suppose a man is sitting on the sidewalk with a big can of milk and every passer-by he ladles out for him a drink of milk, everybody would say it’s a public benefactor, a drink of milk, every passer-by, gives you energy, gives you nourishment.
There's a man that does better than that: for every passerby: he has a friendly smile. That’s better, it helps a person physically more than a drink of milk. It’s healthier for that person to see your smile than to get a drink of milk from you. Take seriously this function that they you have in the world: you must make the world a better place because you're here.