On William Strunk, author of the classic Elements of Style:

His original Rule 11 was "Make definite assertions." That was Will all over.  He scorned the vague, the tame, the colorless, the irresolute. He felt it was worse to be irresolute than to be wrong.

An "irresolute" person is "Undecided or unsure how to act; Indecisive or lacking in resolution."  You couldn’t ask for a clearer demonstration that we prefer overconfident people.