We scare pretty easy. If you're ISIS, you have to look at the national reaction to the attack in CA and feel incredibly powerful, just like OBL likely rejoiced in our reaction to 9/11.
Personally, I feel no different after what happened last week. I obviously hate to see innocent people killed, but there is still a far greater chance that I'd be killed driving to the supermarket, or crushed by furniture.
But I watch TV & listen to the radio, and it seems that my fellow Americans are now terrified beyond belief. What gives on that? Can anyone offer a rational explanation for why that makes sense?