A letter never sent has only one participant but can still change a relationship.

A letter written and not sent has only one participant, and it can still change everything. The writing does something to the writer: it clarifies, releases, and finishes a thought that had been circling. The relationship shifts because one person is now different in it, even though nothing was delivered.

This is a genuinely useful practice. Write the thing you cannot say, to the person you cannot say it to, including people who are gone. Do not send it, or decide later. The point is not communication. It is that some things can only be understood by being written down in full, addressed to the person they are actually about.