It isn't the easiest of tasks to find a short story with a theme of hope.  Yet, I think that Flaubert's "A Simple Heart" is just that.  It is a story in which the main character, Félicité, lives life with a sense of optimism and selflessness.  Her heart is the very best that a human being can possess.  There is a theme of hope in Félicité, herself.  Flaubert constructs her in a manner where there is an earnestness and legitimate goodness in her that helps to revivify the hope one has in humanity.  When George Sand advised Flaubert to start to develop literature of "consolation over desolation," I think that Flaubert understood his friend's advice to be embodied in Félicité.  

Félicité loves without much in way of return.  She demonstrates the intrinsic goodness and does not ask for equality in reciprocation.  She absorbs the cruelty and abuse that others heap on her and never retaliates.  Her death as one through natural causes in which she smiles is reflective of how at peace she is in both her place and the world in which she lives.  It is a short story that captures a sense of hope in humanity.  Part of Flaubert's Three Tales, "A Simple Heart"  is a short story that demonstrates the hope that can exist within human beings.