The plan is a map drawn at your desk. Reality is the street with the construction you didn’t draw.

A plan is made where the information is clean and nothing is happening yet. Reality is where the roadworks are, the one detail nobody could have known about, the thing that only appears once you are moving. That gap is not a planning failure. It is the normal distance between a drawing and a street.

Make the plan anyway, and then hold it as a first draft rather than a contract. Decide in advance what you will do when the first thing goes wrong. Checking the route while you are actually on it beats defending a map that was drawn before you set off.