From Hemingway's True at First Light novel:
Fear is a child's vice and while I loved to feel it approach, as one does with any vice, it was not for grown men and the only thing to be afraid of was the presence of true and imminent danger in a form that you should be aware of and not be a fool if you were responsible for others. This was the mechanical feat that made your scalp prickle at real danger and when you lost this reaction it was time to get into some other line of work.
I love, when in the middle of reading, an unexpected gem appears, and it's something that makes you stop. Read it again. Think about it. Read it again. Think some more, sigh, and move on.