Say what you mean before resentment starts translating for you.

Unsaid things do not stay neutral. They accumulate, and eventually resentment starts doing the speaking for you: through tone, through withdrawal, through a comment that comes out sharper than the situation warranted. By then the original point is buried under the way it arrived.

Say the thing while it is still small and while you can say it plainly. It will feel disproportionate to raise something minor, and that is exactly the right moment. The alternative is not silence; it is the same message delivered later in a much worse form.