The main objective of terrorists is to strike fear into people, not necessarily by the size of the strike but with the "It could happen anywhere to anyone without warning" principal. Their crimes cast fear into the entire population which then puts aside the rational reality that there is but a minute chance of someone actually being a victim, instead it's the fear that takes center stage in peoples minds. The major nations in the world today maintain enough military power to cause serious if not lethal blows to other nations but terrorists don't have this capability so their tactic is the psychology and response behavior of humans.
Now don't get me wrong, 911, the American consulate in Africa, the marine barracks in Lebanon killed thousands and suicide bombers kill hundreds every year, and while at these points of attack they cause substantial damage their strategy isn't about the point of attack itself or the people killed or injured directly, it is about creating a fear that results in a change in public action on a larger scale than their limited physical means could accomplish. The goal of terrorists is to gain power larger than the actual threat they possess by invoking the fear factor over the actual destructive capability factor.
In the aftermath of 911 the U.S., as well as many other countries, adopted policies that drastically altered, restricted or outright banned much of what used to be. Travel by train, ship and especially airline has now become a security web to weave through the likes of which were once reserved for meetings with the President. We have been forced to remove our shoes, change or lose much of the contents of our luggage, disrobe, and spend countless billions of dollars on measures against that remote possibility of the same terrorist act being committed again. Many on the inside believe these measures simply keep the "honest" ones away that, determined terrorists would not involve any of the areas that these measures are designed to guard, the fact is there are far too many other, unprotected opportunities for terrorists to exploit. And when the next act occurs, we will undoubtedly respond as usual by establishing further measures to protect against a similar event that will never be attempted the same way anyway, the terrorists know how we work, they know that once they attack one way all they simply do is move to another target for the next attack, in a way we don’t know so we can’t protect.
They have managed to change our way of life here and abroad in many disturbing aspects well into the foreseeable future, so have they won?