Upvoted, because you make a very important point: I think our best course of action is to accept that these things do happen occasionally. It is very hard to s

Upvoted, because you make a very important point: I think our best course of action is to accept that these things do happen occasionally. It is very hard to stop all zealots, especially if they act on their own or in small groups. Trying to extend spying, restraining ourselves in our free speech, starting to hunt down people of a certain religion, etc. will only have the opposite effect: stifling democracy and free speech. The best reaction is to stay calm and continue to be rational: terrorism exists to instill fear in people. However, looking objectively, the chance of being hurt in a terrorist act is fairly slim in most countries. Especially if the problem is treated well, besides smart intelligence, social improvement: ensuring that kids have a future, talk with them before they radicalize, etc.