What causes human suffering;what seems inevitably tragic about human existence?

What causes human suffering;what seems inevitably tragic about human existence;how one should deal with suffering;what one should learn from an understanding of human mortality.From the Shahnameh your essay will of course focus on Rustem; for Dante, you have many options, but the following characters and their sad stories make especially good choices for the subject (but you can choose others if you wish; just one will do): Virgil, Francesca, Pier della Vigna, Brunetto Latini, Guido de Montefeltro.