I heard this Jewish traditional myth about the Hidden Light on Kristen Tippet’s NPR show On Being. So I went looking for it on da’ net as it was such a wonderful concept and a 
wonderful way of looking at other souls.
On the website Tikkum I found the following article How the Ari Created a Myth and Transformed Judaism
An excerpt:
“How is it that a concept rooted in medieval Jewish mysticism has so endeared itself to contemporary Jews? In order to understand this unlikely development, let us first consider the myth itself, known as “The Shattering of the Vessels” (shevirat ha-kelim).
At the beginning of time, God’s presence filled the universe. When God decided to bring this world into being, to make room for creation, He first drew in His breath, contracting Himself. From that contraction darkness was created. And when God said, “Let there be light” (Gen. 1:3), the light that came into being filled the darkness, and ten holy vessels came forth, each filled with primordial light.
In this way God sent forth those ten vessels, like a fleet of ships, each carrying its cargo of light. Had they all arrived intact, the world would have been perfect. But the vessels were too fragile to contain such a powerful, divine light. They broke open, split asunder, and all the holy sparks were scattered like sand, like seeds, like stars. Those sparks fell everywhere, but more fell on the Holy Land than anywhere else.
That is why we were created — to gather the sparks, no matter where they are hidden. God created the world so that the descendents of Jacob could raise up the holy sparks. That is why there have been so many exiles — to release the holy sparks from the servitude of captivity. In this way the Jewish people will sift all the holy sparks from the four corners of the earth.
And when enough holy sparks have been gathered, the broken vessels will be restored, and tikkun olam,the repair of the world, awaited so long, will finally be complete. Therefore it should be the aim of everyone to raise these sparks from wherever they are imprisoned and to elevate them to holiness by the power of their soul.”
Magnificent