Chance favors the prepared mind.
Today is the dumbest day of the rest of your life. If you’re doing a software project, you should know at least a little bit more about the project tomorrow than you do today, the next day a little bit more, and so on.
Don’t get into detailed decisions and plans at the beginning of the project. Defer decisions to the last responsible moment; that’s when you’ll have the best information available.
Upfront planning is not for the purpose of generating plans, which quickly go obsolete, but for the purpose of creating prepared minds with which to face the uncertain future.