I was reading Arthur The Seeing Stone, by Kevin Crossley-Holland and one of the characters [protrayed as Merlin] mentioned that "Doubt is like rust which corrodes metal. It travels from your brain into your body and eats you away." Then alittle later another quote referring to doubt was "Nothing comes of doubt, except inaction and more doubt." When I thought about these quotes they seemed to be accurate. Doubt does make it harder to do something and it does seem to erode confidence. The other problem with doubt could be that when we hesitate and do not act on what we first think or believe is right, we are not trusting ourselves and this can lead to worries, hesitating and other stress type reactions. Maybe it is these stress reactions that "eats us away."
So, if we don't want to risk getting rusty on our insides, we might want to avoid doubts and second guessing ourselves and worrying about what has or will happen in our lives and ...you get the picture.
Luckily, there are rust removers available.