The next "Aha!" moment came when I was reading The DaVinci Code. I know a lot of people trash the book, and I get it: the characterization wasn't great, the motives were unbelievable, some of the key developments were predictable, and the writing was uninspired. But I will go to my grave defending the plotting of that book. It was a beautifully constructed thriller, where one piece clicked into the next, into the next, into the next. And lest anyone thinks the book was all hook, Dan Brown got sued (although he won) by another author who had basically proposed his EXACT hook 30 years before. It wasn't original at all.
Personally, I don't really want to write the next DaVinci Code. It's just not in my genes to write a book like that. But that book did affect me. It turned me into an outliner. It made me believe that good plots don't happen by accident, that you can't stumble your way into a complex story. It can only happen on purpose. And furthermore, it showed me that people LOVE well-plotted books. The fact that so many millions were able to forgive the DaVinci Code its flaws and still buy it said something.
So this is why, when I'm editing my own work, I'm always asking, "How does this relate to my story? Will this matter later?"
If the answers are "It doesn't" and "No," then buh-buy, it's getting cut.