Terrorism often works better when it is lower scale and less horrific, it is the gradual drip, drip, drip that will get change.
That is the kind of terrorism I fear the most. When terrorists aim for monuments we know what to guard. It is the terrorists who detonate bombs that kill 5 people. But they detonate one every day. And they do it on a crowded city street, a train at rush hour. Then uncertanty comes into play and you start questioning if you're safe steping outside.