The correct version is probably
"Even if you're on the right track
you'll get run over if you just sit there."

Variants include " . . . you'll just be roadkill if you just sit
there" and of course the variant Armitage attributed to MT.

The "even if" quote is routinely attributed to MT and several
others, including even Arthur Godfrey(!). But it probably
belonged to Will Rogers. I cannot cite an original source but
the "even if" quote is attributed to Rogers in, I seem to
recall, _The Boy Who Invented Television_, whose author (again I
think) did his homework. . . .

(Edmon L. Rowell, Jr.)

    "I'm just tryin' to get by being quiet and shy
        in a world full of pushin' and shove."
            --Jimmy Buffett