I think I have written one (or more) to and about every person I ever cared for. If I didn't, it was probably just a passing fancy.
Some of them were given to the person while we were together, some were given to them only after we parted - if we stayed friends. Only a very few were ever kept concealed; and even these I have since published, but without identifying the person who inspired them.
And whether well written or not, I have always felt those written for me were very special because they always revealed feelings that were not expressed in quite the same way as that effort.