The Once and Future King Book 3, Chapter 6
Lancelot is more than just good at knight's games: he is also obsessed with honor. This, ironically, makes the situation at court worse, because even though Lancelot was in love with Guenever, he does not run away with her. To do so would have been simpler, and, it turns out, less destructive. When he returns from the war with Arthur, he asks for a leave of absence, hoping to put Guenever out of his mind entirely.