“Before operating on a patient's brain, I realized, I must first understand his mind: his identity, his values, what makes his life worth living, and what devastation makes it reasonable to let that life end. The cost of my dedication to succeed was high, and the ineluctable failures brought me nearly unbearable guilt. Those burdens are what make medicine holy and wholly impossible: in taking up another's cross, one must sometimes get crushed by the weight.”