I'm reading John Krakauer's "Where Men Win Glory", his book about the life, death and betrayal of Pat Tillman (at the hands of the US Army). While it seems to be affecting me more than I though it would, for now, I'll simply offer this quote found at the beginning of Part 4:
"He who learns must suffer. And even in our sleep pain that cannot forget, falls drop by drop upon the heart, and in our own despite, against our will, comes wisdom to us by the awful grace of God."
- Aeschylus, Agamemnon
You might not agree with it, but for good or bad, I mostly learn through loss.