Someone breaking down after successfully defending the town is not the same as setting up the story. Daryl is ALSO going through this. Michonne was showing signs of maybe going through it. Morgan is in the middle of it. Glenn just killed someone for the first time, so he is ripe to go through it. But hey...sure...throw Carol into that story as well. Might as well do the same thing with her that is being done with the rest of the cast.