自分を疑う人は、敵の軍に参加し、自分に武器を持つようなものです。自分自身が失敗を確信している最初の人であるため、失敗を確実にします。

A person who doubts himself is like a man who would enlist in the ranks of his enemies and bear arms against himself. He makes his failure certain by himself being the first person to be convinced of it.