St. Faustus of Riez ca. 405-490
A ship, after having braved the billows of the open sea, can be in danger even in the middle of what seems the safest port, and is in peril of sinking there. Likewise, in the refuge of religion to which the Savior has led you, do not be without fear; force yourselves, with the help of Christ, to avoid the least negligence, the slightest faults; they act on the soul like drops of water entering a ship’s keel by imperceptible fissures. (Ad Monachos II)