This is the day that goes as expected.
After months of planning almost everything works seamlessly. The only thing that goes wrong is fixed by plan B or C or D, giving you an opportunity to show off your organised contingencies.
The day is a success: You win the medal, make the deal, finish the project, solve the mystery, raise the money or put on the show!
Even the imperfections become anecdotes to laugh about later.
Taking off the twenty kilo-bag of organised worry, you rise weightless to the top of the mountain and enjoy the view of your success.