You have no idea just how true this is. As long as there's a speck of fear, you're on your toes. Just like with electricity. Most of the electrical fatalities are to seasoned electricians who got too comfortable with precedure. I love my P-51 to death!! Next month will be it's 6th birthday. I don't get butterflies with it anymore ... yesterday I came in for a picture perfect landing and forgot to put the gear down ...
As long as you're feeling the butterflies, and your thumb starts to shake as you throttle up, you're doing great!