One tells us what the risk is.
Two confirms what wrong behavior is.
At three, we know the rules, and so can appreciate what the smart third person is doing differently, to break the un- successful pattern and win.
If that folk tale was about just one pig who built a house of bricks in the first place, and the wolf couldn’t get in no matter how he huffed and puffed, where would the story be? Conflict, but no drama, just stalemate. Success for the pig, but no suspense. Anticlimax. No story.
Refer to: Picturebook Study: The Three Little Pigs
Three is suspense, pattern, and contrast, all in one nifty little technique as old as storytelling.
It’s the scientific technique of the variable, with third time lucky.
If somebody fails twice, in similar circumstances, there’s going to be more tension and drama when he tries the third time because we’ve already seen him fail and know it can happen. We know what doesn’t work, we know the situation; now we’re focusing on what he’s doing differently this time. We’re aware of the pattern, the apparent rules, and are concentrating on the one thing that changes.
Instead of two repetitions, you can use the Rule of Three.
The first time the bell coincides with the painful electric shock, you’re too busy being shocked to notice.
The second time, you think uneasily that maybe it wasn’t a coincidence.
The third time, you’ve started jumping before the bell is even done ringing.
If you want your reader interested and involved in the scene before it’s fully begun to happen, there’s nothing like a triple set- up to get things rolling. It gives added drama. It directs the read- er’s attention where you want it directed. And it makes the scene’s meaning clear in a way it could not have been in isolation.
Choose and control the variable with care, keep the situations visibly comparable so the reader will be aware of the bell/ shock pairing and be anticipating the outcome, and all three scenes will gain in impact and effectiveness.
From Anson Dibell’s book on writing called Plot