I would say this: sometimes, and more and more, keeping yourself safe at home means going to the problem before it comes to you. That's why we are in Afghanistan. Frankly, the problem came to us. We need to make sure we don't get more problems from there.
It's not just that kind of problem. Libya also would have just metastasized into a bigger problem. Kosovo would have metastasized into a bigger problem had we not gone to it. Waiting for the problem to come to you in a globalized world is simply to fail.
I agree that sometimes you need to go away. Security at our borders sometimes requires going to someone else's, but only when it's our security that is directly threatened. We do not want to give the idea, to anybody, that NATO is sort of gallivanting around the world trying to solve everybody's problems. We're not. When there is a clear and direct threat to us, we can't wait until it strikes us.