Some people might say it takes a rare individual to realize that they utterly unimportant and ordinary. I don't think this realization is particularly rare. The reason people laugh at the guy who raises his hand and says "I'm not" in that scene from The Life of Brian is not just the incongruity of a single person standing out from the crowd by being the only one to say they don't stand out. Most people, I think, recognize at some level that we have all been in that crowd, that we are all in crowds of one sort or another at all times, and that Dennis (the "I'm not" guy) is right when he says he's not different. He's only saying what is true for any of us, and which we already know (but saying it with impeccable timing).
Then again, my friends tell me I am an optimist.
"True wit is nature to advantage dressed,
what oft was thought, but never so well expressed."
-- Alexander Pope
In broad strokes the actions of any of us are both incredibly predictable and completely inconsequential. People who know me well might be surprised to hear me say that, as I also believe strongly in the value of each human being (or other sentient entity), and in seeming contradiction to the above, the uniqueness of each person. But the difference is in scope. Each of these ideas (that we are unique individuals of great value and that we are interchangeable particles in history of no individual consequence) can be true as the same time of the same person, because they address different scales. On the scale of history I certainly do not matter. To proclaim otherwise would be hopelessly grandiose. Even limiting ourselves to the here and now I do not matter to such a large segment of humanity that, by any objective measure, I might as well not exist. Even the actions of the rich, powerful and famous will disappear into history. If Newton had died in childhood Leibnitz would have gotten credit for discovering calculus, and life would go on. Even those things which seem overbearingly huge to us right now are hiccups in history, and it will all be gone in the blink of an eye, as the Atlantic grows just a few meters wider.
However, there is another scale, the human scale of one to one interactions, with my friends, colleagues and even random strangers on the internet. In that tiny circle around each of us, we do matter and we are unique, important individuals. And, after all, we each live in a universe of our own, centered, by necessity, on ourselves.
People deal with this in different ways. Most of us, most of the time, just ignore the big picture, because, in the end, it ignores us. Periodically someone will be outraged that nobody around them 'realizes' how utterly banal it all is, they will rant and shout, or mope and groan, or perhaps take up 'mischief' (also known in some circles as 'wankerhood') in order to wake people up. And the raging individuals, too, are part of a crowd, gnashing their teeth and shaking their fists in unison.
There is no escaping your insignificance. A few decades as a single speck out of billions swarming over a mote lost in space. There's no significance in that, no matter what you do, if you insist on taking that kind of perspective.
But nothing requires you to take that kind of perspective. There is nothing more natural about looking at your life through a backwards telescope from the surface of the moon. The distance between your thumb and forefinger is just as natural a measure as any other, and the few hundred people you know are no less significant that the billions you do not. You are the center of the universe. There is no escaping your importance and responsibility.
This, too, is not a unique realization, but one that is useful to remind ourselves of from time to time.