"And G-d said:  Let there be light!"

The Midrash compares G-d's creation of the universe to the work of a human architect.  When a person wishes to build something, first he fixes his purpose in his mind.  Then he starts his labor.

"Let there be light" was the first statement in creation because "light" is the true purpose of existence:  through the study of Torah and the fulfillment of mitzvot, Divine radiance is revealed.

"Light" is the purpose of existence as a whole.  Further, each individual is a microcosm of the world.  "Light" is therefore the purpose of each Jew:  that he or she transform his or her situation and environment to light, goodness, instead of darkness.

If light is the purpose of every created thing, it follows that it must also be the purpose of darkness itself.  Darkness does not exist only in order to be conquered or avoided, thereby presenting man with a choice between good and evil; the fulfillment of darkness is when it is changed, when the bad becomes good -- when darkness is transformed into light.

The problems that we meet in life might sometimes make us despair even of winning the battle of light over darkness, let alone of turning the bad itself into good.  But with the words "Let there be light!" the Torah presents the goal for each of us as individuals and also for humanity as a whole.  This is the Divine purpose for our existence:  and if this is G-d's purpose for us, there is no doubt that we will be able to succeed!