The words spoken most easily are not always the words needed most urgently.

Fluency and necessity often point in different directions. The sentences that come out smoothly are the ones you have said before, and the one that matters is usually stuck somewhere behind them, awkward and unrehearsed. Ease of speech is a sign of practice, not of importance, which is why a conversation can be full of talk and still be missing the thing.

Ask yourself what you have not said to someone you see often. If a sentence makes your chest tighten slightly, that is a reasonable indicator. Say it badly rather than not at all; the wording matters much less than you fear.