I always thought that wish-granting is instant, even if the effects of that wish are delayed.

So if I wish for something to happen in 5 days, it's granted in the moment and guaranteed to happen. That raises a question though: Can I wish to cancel a wish I have already made, but whose effect has not yet taken hold? On its face, this should be possible, but if we take it as a given that all valid wishes are always granted at the moment of utterance, then it might be physically/psychologically impossible for me or anyone else to revoke the wish before its IRL effect is complete.