“G-d said, ‘Let there be light’ and there was light.” 
As Torah says, this wasn’t sunlight or other physical light. This was Divine, spiritual Light; the Kabbalists call it “Or Ein Sof” — “The Light of the Infinite.” It surrounds and permeates all Creation. In our natural state — the state of Adam and Havah (Eve) before they ate the forbidden fruit — this Light is part of our ongoing experience of being alive:
“…Rabbi Elazar said: ‘[In] The light which the Holy One created on the first day, Adam saw…from one end of the world to the other.” 
In this Light, we experience our truest Peace, our truest Joy. Any lack we feel — love, money, fame, success, material goods, and so on — is really the lack of this Light. In all our greed, in all our aggression, in all our desperateness to acquire, it’s really Divine Peace that we’re seeking.
Yet — that Light is always with us:
“When the Holy One considered the generation of the flood and the generation of the dispersion, and that their works were vain, He took it from them and concealed it for the upright in the world-to-come.” 
“Concealed [the Light]?” The rabbis mean: Rather than withdrawing it completely (ending Creation altogether), or allowing Divine Light to be seen as freely after wrong-doing as before (encouraging even greater wrongdoing), G-d allows Light to be obscured by wrong-doing, but keeps It always available to those who seek It.
Only “in the world-to-come?”
No. G-d can be known in this world, too.
“Faith is based on revelation, but a revelation that takes place every day [in this world].” 
Torah tells us that G-d, and G-d’s Light, can be found in this world; in our world — in our lives — too. The Light can be found by the “upright” or “righteous” in every generation, as Rav Kook taught:
“When I lived in London, I used to visit the National Gallery, and my favorite pictures were those of Rembrandt. I really think that Rembrandt was a Tzadik [a “righteous” or “upright” person]. Do you know that when I first saw Rembrandt’s works, they reminded me of the legend about the creation of light? We are told that when G-d created light, it was so strong and pellucid, that one could see from one end of the world to the other, but G-d was afraid that the wicked might abuse it. What did He do? He reserved that light for the righteous when the Messiah should come. But now and then there are great men who are blessed and privileged to see it. I think that Rembrandt was one of them, and the light in his pictures is the very light that was originally created by G-d Almighty.” 
Only “the upright” or “righteous?”
Does G-d, kind beyond imagination, give Good to some, and withhold it from others?
That belief itself separates us from Light.
G-d gives Good to all, always.
Light is there for us, if we want it. And with it, Peace and Joy. Peaceful joy, Joyous peace. It is part of what we are.
We might first experience Divine Light in meditation or prayer. What are these but the moving of our attention from the ordinary thoughts and feelings that take up our minds, to the wider field of our own Divine existence?
Gradually, it becomes easier to alter the direction of our attention; Peace, Joy and Light become embedded in the daily experience of our minds and hearts.
They were never really absent.
Who, then really conceals the Divine Light from us? G-d?
We do, ourselves:
“Your sins separate you from G-d.” 
In Hebrew, “sins” are “mistakes.”
With G-d’s help, all mistakes are correctable.
It’s why “repentance” in Hebrew (“teshuvah”) really means “return.” It’s a return to our true natural state — seeing Divine Light, with its Joy and Peace, in our lives every minute, every day. It’s a return to what and who we really are.
We’ll see Divine Light long before we’re ever finished “correcting” ourselves.