When writing a plan, assume that you are using disappearing ink. A special disappearing ink that will slowly fade over time. To ensure that you don't lose your plan you have to keep rewriting it.
Now, hopefully you'll realise that it doesn't make sense to keep rewriting the same thing if it no longer applies. Therefore, you'll be forced to update it as you rewrite what has faded.
Hmm. I wonder if there's an application in this?