Rule 383.3.e.2

If the Triggered Ability says “you may” or “they may” as the first part of its effect, its controller has the choice of whether or not it is performed.

• 383.3.e.2.a During finalization of the Triggered Ability, the player who controls the Triggered Ability may choose to perform it.
• 383.3.e.2.b If they do not, it is removed from the chain. Example: A player controls a unit that reads in part “Once each turn…

Official Core Rules