What distinguished dishonorable flight from the "safe and honorable withdrawal" which Charny thought all good men-at-arms needed to learn to execute?
Joinville, writing of events about a century earlier, gives a concrete example of the tension between tactical prudence and fear of dishonor, when Joinville and his companions found themselves heavily outnumbered:
I and my knights clapped spurs to the rescue of Lord Ralph of Wanon, who was with me, whom they had pulled to earth; and whilst I was on my way back, the Turks pinned me down with their spears. My horse, feeling the weight, fell on his knees, and I passed on between his ears, and picked myself up with my shield round my neck and my sword in my hand. Lord Erard of Syverey,—God rest his soul!—who was of my company, came up to me, and said, that we had best draw off to a ruined house, and wait there until the King should come. And as we were going along on foot and horseback, a great horde of Turks broke upon us, and bore me down, and passed over me, and snatched my shield from my neck; and when they were gone by, Lord Erard of Syverey came back to me, and led me along, till we reached the walls of the ruined house; and there Lord Hugh of Scots rejoined us, with Lord Frederick of Loupey, and Lord Reynold of Menoncourt.
There the Turks attacked us on all sides. Part of them got into the ruins, and thrust at us with their spears from above. Then my knights desired me to take hold of their horses' bridles, which I did, to prevent the horses from stampeding; and they warded off the Turks so vigorously, that they were praised by all the champions of the army, both by those who saw the deed, and those who only heard it told.
There Lord Hugh of Scots was wounded with three spear-wounds in his face, and Lord Ralph too; and Lord Frederick of Loupey was wounded with a spear between his shoulders, and the gash was so wide, that the blood spurted out of his body as through the tap of a cask. Lord Erard of Syverey got such a sword-cut across his face that his nose hung down onto his lip.
Then I bethought me of Our Lord Saint James: "Fair Lord Saint James,"—I prayed, "Help and save me in this need!" No sooner had I made my prayer, than Lord Erard said to me:—"Sir, if you thought it would be no reproach to me and my heirs, I would go and fetch you help from the Count of Anjou, whom I see yonder in the fields." And I said to him:—"Sir Erard, methinks it would be greatly to your honour, if you were to fetch us aid to save our lives, for truly your own life is in danger." (And indeed I spoke the truth, for he died of that wound.) He asked the opinion of all my knights who were there, and they took the same view as I did; and thereupon he asked me to let go his horse whom I was holding by the bridle along with the rest, and I did so. He came to the Count of Anjou, and begged him to come to the assistance of me and my knights. A rich man who was with him would have dissuaded him, but the Count of Anjou said he should do what my knight asked him; and he turned rein to come and help us, and several of his serjeants spurred on ahead; and when the Saracens saw them coming they let us be. In front of these serjeants rode Lord Peter of Alberive, sword in hand, and when he saw that the Saracens had left us, he charged a whole heap of Saracens who had got hold of Lord Ralph of Wanon, and rescued him, sorely wounded.
This account also gives a sense of why retreat was such a serious issue for men-at-arms: Joinville, dismounted, had to hold the horses' bridles to keep them from running. There must have been many times in battle when a horse began to carry a rider away from the enemy despite the best efforts of the man: how tempting it must have been to just keep going.
Joinville, J., & Bowen-Wedgwood, E. K. (1906). The memoirs of the Lord of Joinville: A new English version. New York: E.P. Dutton.