Perhaps we should enjoy the synchronicity. Perhaps we also should find solace when we know we're writing who we are, infusing ourselves and our experiences as deeply as possible into our words, delivering our own takes on what has "already been written," even if we may be unaware at the time that it has.
Margaret Dornaus sums up this situation well in a post, "Revisiting déjà-ku . . .," at her Haiku-doodle blog. So I won't say anything more here and will let you read her beautiful words.