Mt 5:13-16
[Jesus said to his disciples:] 13“You are the salt of the earth. But if salt loses its taste, with what can it be seasoned? It is no longer good for anything but to be thrown out and trampled underfoot. 14You are the light of the world. A city set on a mountain cannot be hidden. 15Nor do they light a lamp and then put it under a bushel basket; it is set on a lampstand, where it gives light to all in the house. 16Just so, your light must shine before others, that they may see your good deeds and glorify your heavenly Father.”
You are the salt... the light: It is said that ancient peoples believed that when we face God, he will ask us only two questions.
First: Did you find joy in your life (salt of the earth)? Well, if you had no joy, chances are neither will you find it in heaven. You may just spread grouchiness up there and you may be asked to go down instead.
Second: Was your life a joy for others (light for others to see)? We do not create joy for ourselves. We bring joy to others and in the process we find joy in our hearts.
A young puppy is going round and round trying to catch its tail. An old dog watches him. Then the old dog speaks: “You know, when I was young, I used to try to catch my tail hoping that it would give me joy. And I always failed. I later discovered that just as long as I lived through life, my tail was sure to follow me!”