What some say of rooted faith, fides radicata, that it continues, while weak faith may come to nothing, seems to be contradicted by this Scripture; for, as the strongest faith may be shaken, so the weakest, where truth is, is so far rooted that it will prevail. Weakness with watchfulness will stand, when strength with too much confidence fails. Weakness, with acknowledgement of it, is the fittest seat and subject for God to perfect his strength in; for consciousness of our infirmities drives us out of ourselves to him in whom our strength lies.
-- p. 96, The Bruised Reed by Richard Sibbes
Sorry, I don't know what that "fides radicata" means either, but you get the gist of this paragraph, don't you?