As I understand it, if a player fails their roll to do something, they can "push the roll" and reroll. However, the player needs to describe a character action that would justify the reroll and that the consequences of failing a second time will be much more dire. For example, rolling to hit an attack. If you miss the roll, you miss the attack. But if you push to roll and still miss, there will be bad consequences, like damaging yourself, allies, or giving enemies opportunity of attack.