People spend their whole lives looking for meaning, trying to find something that will justify their existence and give them a reason to continue working and striving, to continue fighting for what they know is right and not to give up even when it seems as if everything is falling down around them. We often have such moments when we are ready to give up because nothing is going right and it looks like all our efforts are worthless and bring no results. As we realize the insignificance of a single human life in the context of the entire world, we despair and make the mistake of thinking that what we do does not matter.
There is an interesting passage about it in Chaim Potok's The Chosen. Chaim Potok is a brilliant writer and I really enjoy his books for their depth and their understand of human (and particularly religious) nature. I love the way he explores issues that relate to our religious community and have meaning for us, and his novels are so easy to get into because we can connect with the characters based on our own experiences.
Reuven, the protagonist of The Chosen, is worried because his father is putting what he feels are unnecessarily long hours into his work and his efforts to support a Zionistic state (this takes place before the establishment of the state of Israel). His father works late every night and barely sleeps, and when Reuven sees that it is taking a toll on his health, he feels the need to protest and to urge his father to see the doctor and to "take it a little easy." This is his father's response:
"Human beings do not live forever, Reuven. We live less than the time it takes to blink an eye, if we measure our lives against eternity. So it may be asked what value is there to a human life. There is so much pain in the world. What does it mean to have to suffer so much if our lives are nothing more than the blink of an eye? ... I learned a long time ago, Reuven, that the blink of an eye in itself is nothing. But the eye that blinks, that is something. A span of life is nothing. But the man who lives that span, he is something. He can fill that tiny span with meaning, so its quality is immeasurable though its quantity may be insignificant. Do you understand what I am saying? A man must fill his life with meaning, meaning is not automatically given to life. It is hard work to fill one's life with meaning. That I do not think you understand yet. A life filled with meaning is worthy of rest. I want to be worthy of rest when I am no longer here."