From Neil Gaiman's American Gods, a novel that explores the gods that people brought with them to America, and then forgot. The following quote comes in a discussion of how stories can allow us to safely experience the problems of others (bonus, quote includes a bit of etymology):
No man, proclaimed Donne, is an Island, and he was wrong. If we were not islands, we would be lost, drowned in each other's tragedies. We are insulated (a word that means, literally, remember, made into an island) from the tragedy of others, by our island nature, and by the repetitive shape and form of the stories. The shape does not change: there was a human being who loved, and then, by some means of another, died. There. You may fill in the blanks from your own experience. As unoriginal as any other tale, as unique as any other life. Lives are snowflakes -- forming patterns we have seen before, as like one another as peas in a pod (and have you ever looked at peas in a pod? I mean, really looked at them? There's not a chance you'd mistake one for another, after a minute's close inspection), but still unique.
Without individuals we see only numbers: a thousand dead, a hundred thousand dead, "casualties may rise to a million." ...
We draw our lines around these moments of pain, and remain upon our islands, and they cannot hurt us. They are covered with a smooth, safe nacreous layer to let them slip, pearllike, from our souls without any real pain.
Fiction allows us to slide into these other heads, these other places, and look out through other eyes. And then in the tale we stop before we die, or we die vicariously and unharmed, and in the world beyond the tale we turn the page or close the book, and we resume our lives.
But then I read an article in this month's Wired about how our friends and family's behavior greatly influence things like our weight and our ability to quit smoking:
An obese sibling hundreds of miles away can cause us to eat more. The individual is a romantic myth; indeed, no man is an island.
I think both ideas are right. People shut out the pain of the greater world, because it is too much to bear. But they also allow the pain (and the joy) of their family and friends onto their islands, because that is what friends and family do for each other. Maybe each man is an island, but an island in an archipelago of our loved ones.
And here's a fuller etymology for insulate, from the OED: "from Latin insula, meaning island, + -ATE, or from insulatus. The verb insulare is not recorded in late or medieval Latin, but may have existed in the latter or in Renascence Latin; the corresponding Italian isolare ‘to reduce into an island’ is known in 16th century."