Here at our little garden spot deep in the heart of Iraq we no longer react to explosions for the most part. You see the Explosive Odinance Disposal range is right in front of the hangar in which we live and work. This results in 10-15 "controlled blasts" each and every day. This is so commonplace that we are no longer able to tell if the explosions are from incoming mortars (also common but poorly aimed) or from the EOD folks.
The common reaction here is to look around when something blows up, check to see that you are still alive (yup), and continue working. If the blast was a mortar then the siren will let you know within a minute or so and you can go inside and wait it out with everyone else. This process of desensitization takes all of 1-2 days from arrival. You really can get used to anything.