The sort of power that one wields as a SCOTUS justice is akin to the sort of power that one wields when one carries a gun, in the sense that it gives you the power of live and death over others. The power of a judge is more subtle and less direct, but it's still power beyond that which a normal person possesses.
People with great power in their hands (whether it be in the form of a gun or a pen) wield it according to their own character.
Most people, if you put a gun in their hands, will (hopefully) realize that it is the power of life and death over others, and will treat it with the respect it is due; immature folks in that situation might be more inclined to (for instance) pick a fight, feeling like they're invincible. But as they mature, if they have honor, they will use that power in an honorable way: for the defense of the innocent. If they lack honor, they will use the power to coerce others for their own interests.
A new-fledged Justice might be not unlike the immature gun-owner: she might at first be more inclined to rule in arrogant ways, simply because of the lack of accountability. But as she matures into her role, her ultimate position will be determined by the sum of her personal honor and character: If she has those qualities, then she will wield her power with honor. If she lacks them, she will not.
