Letters (that were never sent) >>on hold<<

We all have our secrets, which we maybe can't tell anybody. Sometimes we are about to share them, to get rid of the weight on our shoulders, but our mouth just won't obey and we can't. We just can't.

But if we told someone, maybe that would change our life. Who knows......

What if there were characters in the Wizarding world who had such secrets, who wanted to tell somebody, who maybe wanted to send a letter to confide in someone. But they never did, so we never found out about it.
What if there were letters in the Wizarding world, that were never sent, but which could have changed the whole history of magic as we know it?