The deepest, most soul-crushing of tragedies that can befall man are those from 'silly' causes. Something that works as a matter of routine for everyone so much that it's not even a thought that crosses your mind, but alas, a trivial random event so fully exposes the horrific fragility of being human.
Tragedies stemming from acts of God or 'great' events that feature in a long-arc narrative, or as identifiable to some deep cause, are relatively 'manageable'. It takes superhuman mental strength to deal with an event unique to you in impact, but is unclassifiable to most other people. The enormous guilt that comes with it, with a post-mortem of every decision that lead to it no matter how far away back in time or relevance, no matter how deceiving the clarity of hindsight; the constant reminder of what could have been; the constant self-flagellation, ... I shudder at the thought.