Reflection.
I was thinking about parakeets earlier. Yes, the tiny little birds that amiably pass their time by affectionately pecking at their own reflection in a mirror. They, just like us, can die of a broken heart. If they have experienced love in their life; attention, affection, something outside of themselves...If they have that, and it is taken away, they have nothing left. Nothing except that mirror that used to draw their pleasure and excitement. All of a sudden the mirror doesn't hold the attraction it once did. And what is left except for a broken heart and the deep pit of depression.
The "shiny" things we hold dear, the things of most importance, they can change or be taken away in an instant. What is important in this life? What will future generations remember about us, if anything? Even if we are influential in this life, what does that really matter? Doing right does not guarantee that what is right will be done back. In fact, it quite guarantees that it won't. Why should we look past that shiny mirror? Yes, we may find even more happiness and fulfillment behind that mirror, but in almost every circumstance, it will be so much more painful than if we'd just settled for entertaining ourself with that empty mirror. We could happily spend our days adoring the perpetual mirror, but there is more pain to our existence than that. Why?