Rule 27 of 32 · Chapter V — Carry, Don't Control
Keep the promise after it has become inconvenient.
Why this rule exists
Every promise is cheap when made and expensive somewhere later, and the later cost is the only part anyone actually observes. People do not build their plans on your intentions; they build them on their estimate of what you will do when honouring your word costs you something. One abandoned commitment resets that estimate for years.
In practice
Promise less than you want to at the moment of enthusiasm, then treat what you did promise as load-bearing. When the cost lands, pay it and don't itemise the bill for the other person. If you genuinely cannot deliver, say so as early as you know, offer a replacement, and never make them chase you for the news.
When it doesn't apply
A promise made on false information, or one that has become a way to harm someone, should be broken openly and quickly — stubborn consistency is not integrity when the facts have changed underneath it.