A couple of extra notes...
1 - I sometimes sing to Mia. It is hard to stay tense if you are singing "A Four-legged Friend" - although Roy had a better voice than mine.
Fears are not strictly rational. For example, when flying over Iraq, I found I was not afraid of being shot at. That is just as irrational as being afraid of the wrong thing - but to me, it felt like I was in a movie, and I was waiting to see what the ending would be.
A good book on how our minds work and how fear can be present or absent is Deep Survival: http://www.amazon.com/Deep-Survival-Who-Lives-Dies/dp/0393326152/ref=sr_1_1?s=books&ie=UTF8&qid=1331565382&sr=1-1