Never fall in love with your plan.

Rule # 11.

A subset of the - ubiquitous in the Marine Corps - quote "No plan survives initial contact with the enemy." Which Google tells me should actually be:

“Therefore no plan of operations extends with any certainty beyond the first contact with the main hostile force.”

- from Prussian Field Marshall Helmuth von Moltke in the mid-nineteenth century.

Regardless. Applies to everything. Plans don't mean anything.