The rest of the sentence calls fear a nameless, unreasoning, unjustified terror that paralyzes the effort to turn retreat into advance. He is diagnosing a psychology of the Depression, not forbidding caution. He had been unable to walk unaided since polio in 1921, and he arranged the inauguration so that the country would not watch him struggle to the lectern. The sentence is about a paralysis he understood in more than one way.