A Supreme Court justice must be many things all at the same time.
Justice Roberts once described his job as being an Umpire that can call balls and strikes, that is, an apolitical arbiter that can politely work with the other judges to come to informed and wise decisions on a wide matter of law.
A Judge should be empathetic, learned, and cautious. Their rulings are capable of affecting the lives of many and Judges rule on final death row appeals.