It seems as if our writers’ minds are working all the time.
Take your third act, for example. Everything you’ve outlined and drafted from the start results in shifts in your story, and your subconscious writer’s mind is keeping track of it all, each interwoven strand, keeping the sense of the whole story. This way you take some small but important aspect of the beginning and with it affect something vital at the end, which will resonate throughout your tale.
One great example you’ll remember from Lord of the Rings. Bilbo’s kindness in not killing Gollum, who would have killed him, is echoed repeatedly in Frodo’s less certain relationship with the wicked creature, and at last forces the outcome of the third act showdown.
Do you remember the posy of unusual flowers Allaigna received from a stranger in Verse 4 of Allaigna’s Song (Pulp Literature Issue 2), which comforted her when she was alone in the woods in Verse 13 (PL #5)? Without too many spoilers I can let you know you’ll see it again in Issue 8 and further down the road, its significance growing each time it appears.
Isn’t it grand how much our writing minds know? We learn these things instinctively as readers, but grow even more as writers as we employ our craft over and over on scales as small as a clever word choice and large as the whole world we created.