You gave your word before you knew it would cost more. That’s exactly when a word is worth something.

Promises made while they are cheap are not promises yet, they are predictions. The moment the price goes up is the moment your word starts meaning anything, because keeping it now requires something from you. That is uncomfortable, and it is the entire point. Anyone can be reliable while reliability is free.

If you are carrying a commitment that got heavier, do the thing rather than quietly renegotiating it in your head. If it has become genuinely impossible, say so early and directly to whoever it affects. The slow fade where nobody says anything is the version to avoid.