What Will You Always Yearn For?

Life is full of happiness, though it’s human nature to never be satisfied.

Why did Hashem create only human beings with such a flaw in this mechanism? After all, animals don’t express dissatisfaction. The answer is that human beings are created with a yearning to see Hashem. They once saw Him before they were born, and want to see Him again. If they cannot, they won’t be satisfied. — Most Beautiful Nation