The material and moral consequences of every major battle are so far-reaching that they usually bring about a completely altered situation, a new basis for the adoption of new measures. One cannot be at all sure that any operational plan will survive the first encounter with the main body of the enemy. Only a layman could suppose that the development of a campaign represents the strict application of a prior concept that has been worked out in every detail and followed through to the very end.
Helmuth von Moltke the Elder
This quote has been paraphrased, and shortened to now be,
No plan ever survives contact with the enemy.
While it is intended to be for military strategists, it can be used by the rest of us.
We face an enemy every day, and that enemy can and does want to disrupt our plans.
The main enemy we face is time.
No one knows how much we will be given, and any time wasted cannot be reclaimed.
Another enemy, we face daily is distraction.
They will do everything they can to disrupt our plans, and to lose sight of our goals, and higher purpose.
We cannot allow ourselves to be taken captive by either.
