In terms of the ego, most religions teach in some way that all of us must die before we die, and then we will not be afraid of dying. Suffering of some sort seems to be the only thing strong enough to destabilize our arrogance and our ignorance. I would define suffering very simply as whenever you are not in control.
Things Hidden: Scripture as Spirituality (ed. SPCK, 2016) - ISBN: 9780281075171