I did a bit on plotting last Friday but while reading On Becoming an Author, John Gardner, I read a sentence that resonated with me. "Plot is not a series of surprises, but a series of recognitions or moments of understanding." Sometimes when writing and struggling to get the words on paper, I know there are moments when I suddenly see what I was meaning to say. That often means going back and removing a scene or a short passage that jumped in when it brought no understanding to what I was meaning to say.
Sometimes the writer knows what they mean but they've managed to obscure the understanding from the reader. Not letting the reader know what's coming and blindsiding them can make them turn away from the story. Try to think of the reader as a partner and let them in on the secrets you hold from the characters. Leave the surprises for the characters to reach a moment of recognition or understanding.