Be like a solid tower whose brave height remains unmoved by all the winds that blow; the man who lets his thoughts be turned aside by one thing or another, will lose sight of his true goal, his mind sapped of its strength.
Open your mind to what I shall disclose, and hold it fast within you; he who hears, but does not hold what he has heard, learns nothing. Beatrice - Canto V 40-42
They had their faces twisted toward their haunches and found it necessary to walk backward, because they could not see ahead of them. ...And since he wanted so to see ahead, he looks behind and walks a backward path.