If the instruction to Pay resources is part of paying any other cost, choosing not to pay those resources will prevent the execution of the associated effect. See rule 201. Costs for more information.
§ 444.2.b Core Rules PDF (officieel)
§ 444 Pay
§ 444.2 When a player is instructed to Pay a resource, that player may remove that resource from their Rune Pool if it exists there. If they choose not to, the instruction is ignored. Example: When Diana, Lunari’s triggered ability resolves, if its controller has [1] Energy in their rune pool, they choose w…
