Before undergoing a surgical operation, arrange your temporal affairs. You may live.

Bierce plays on the usual advice. Everyone expects the warning to say you may die, so you should put your affairs in order. He says instead that you may live, and he delivers it as if it were the more alarming possibility. The joke comes from his deadpan, sardonic style. He was a journalist and satirist, best known for The Devil's Dictionary, and he liked to turn comforting assumptions upside down. Here he suggests that survival is the outcome people are least prepared for, and that it comes with obligations: bills, relationships, unfinished work. (The line is widely credited to him, though I can't point to its exact source.)

Under the humor is a practical point. We tend to prepare for the dramatic outcome and forget the ordinary one that is far more likely. Someone facing a scheduled operation might write a will and name a healthcare proxy, which is wise. But they should also arrange time off work, set up bill payments, and ask a friend to help during recovery. Planning for life, in other words, matters as much as planning for death.