Remember when Michonne wrote a message on her arm to David to tell him that she'll get him home so that he can say goodbye to his wife before leaving this world? Yeah, that promise was instantly forgotten once David met his demise at the hands of a batch of walkers. We see Michonne spot the writing on her arm but then nonchalantly wipe her arm clean. Sure, some could call out Michonne for being so easily forgetting of what's just happened, but that is the world the show now inhabits. These things are easy to forget and the world goes on, regardless of what was said and what was done.