The attack last week on a pop concert in the UK was upsetting to say the least. If you live in Orlando, you haven't forgotten about the Pulse shootings, either. Whether or not that was a terrorist attack of a home-grown crime doesn't matter. It's a scary, sad, anger-inducing thing.
Terrorism is a last resort disruption that acts in a way that a full nation can't. A terrorist organization can't destroy another nation with its air force and navy, or a well organized force of a hundred thousand people. If it's an organization at all, it doesn't exist as a member of any world order. Because it doesn't have that power, and make no mistake, it's about power and not religion, it has to improvise and look for other ways to affect the world. The actual damage it does is usually symbolic and rarely devastating relative to other things we can't control (especially natural disasters). The symbolic damage is really good at creating fear.
Fear is a powerful motivator, and it influences our decisions. We don't try to cross an 8-lane freeway on foot, because fear makes the powerful suggestion that we might not survive. It's a useful mechanism in that case. On the other hand, sometimes fear just gets in the way. When we're teenagers, we're afraid to talk to people we want to see naked because, well, just because. Nothing bad can actually happen beyond being disregarded by the people we desire, but this generally does not result in a fatality.
John Q. Terrorist can't outright destroy a functioning nation by way of brute force. He doesn't have the resources. But if he's patient, he can set things in motion to have it destroy itself. Because fear is such a powerful motivator, it can cause people to have strong feelings of distrust... toward each other, toward the government, to people not like us. The United States already has this seed in place, because despite 200 years of slow progress, we're still not over racism. As a society, we've managed to marginalize this to an extent, but not enough to avoid electing an authoritarian who takes advice from a white nationalist. It started before that, even, when through two presidents, of different parties, we allowed our freedoms to be eroded through domestic surveillance programs. I thought the Brits were more evolved than us, but they too think they can go it alone, by leaving the EU.
The terrorists don't win by killing people, they win by getting us to tear ourselves apart.
Let me frame it a little differently, though. If you're an American, your odds of being killed by a refugee terrorist in the US is 1 in 46 million. The odds of being killed by an illegal immigrant terrorist are 1 in 138 million. Now, because I'm going for perspective, know that the odds of dying in a car accident are 1 in 113. Think about that. If 9/11 happened once a month, getting in your car is still exponentially more dangerous. Are you scared of getting in your car?
Your fear of terrorism is irrational.
When you change your behavior, engage in fear of people who look different, elect people with a nationalist or isolationist agenda, you are giving the bad guys exactly what they want. I'm not suggesting that we become flippant about the real problem of terrorism, but the reality is that most of us are not affected by it, and likely won't be. Don't give the bad guys what they want.