Words become expensive once trust begins charging interest on them.

Once someone has learned that your words may not hold, everything you say afterwards has to be checked against the record. The statement itself is no longer sufficient; it now carries the weight of past ones. That is the interest being charged, and it is paid on every sentence rather than only on the one that failed.

So be careful about what you promise casually, especially the small things, because those are where the record is mostly built. If you have already accrued some of this debt, it is repaid the same way: not with explanations but with a long stretch of saying and doing the same thing.