"No plan of operations extends with any certainty beyond the first contact with the main hostile force."
- Helmuth von Moltke the Elder
It's important to have a plan. Without a plan, you won't know which way to go or which actions to take in order to achieve your objective. It's also important, however, to be able to adapt that plan to meet the changing situation that you're facing.
"Everybody has plans until they get hit."
- Mike Tyson
It took me a long time to be ok with having to change my plans. I felt like any change to my original plan signaled a failure on my part in some way and thereby I was a failure. I had the idea that if things didn't go exactly as I had anticipated, that the whole endeavor was a lost cause.
"A good solution applied with vigor now is better than a perfect solution applied ten minutes later."
- George Patton
I've come to learn that being able to change the plan is a good and necessary skill to possess. In fact, any endeavor worthy of having a plan in the first place is going to be necessarily complex enough that you probably won't be able to consider and account for all the possible conditions and outcomes. Instead of trying to predict every scenario, which is a silly thing to even think of being able to do, just be flexible. Adapt.
Adapting the plan to the reality that you're faced with is not a failure.
It does not mean that you've lost the battle.
Failure occurs when you quit trying to achieve the objective of the plan. When you give up on the reason for having a plan in the first place, that's when you've failed. Having to change the way you approach the objective doesn't mean you aren't going to get there, it just means that the way you have to take a different route. You're never going to be able to foresee every situation and condition. You're never going to have the perfect plan. Make friends with that fact and work with it, not against it.