CNN terrorism expert Peter Bergen

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Despite the lack of a recent major attack within our borders, Peter says we cannot easily ignore the intense threat of another terrorist attack. "This is a guy who doesn't take vacations or weekends," he says. "He's a full-time terrorist and he wants to destroy the United States. If he could, he would."

Peter believes we "absolutely" will be attacked again. "What form of attack it will be, when it will be, I can't tell you. But al-Qaida isn't going to decide one day, 'Oh, the United States is so great.'"

Peter says one of the biggest dangers is that, to some degree, Americans have lost sight of the lessons of 9/11 and have lost vigilance against those who wish the country harm. "Americans have many virtues, but patience is not usually one of them," Peter says. "Our enemies are incredibly patient; for them this is a generational warfare. For us, we think about this year, maybe the next election cycle. These guys are thinking in terms of a hundred years of battle against us."