Sometimes, what the writer writes comes across differently than what the writer means. Not necessarily because of a poor choice of words but perhaps more due in part to the readers perceptions and their own experience.
In fact, I'd venture to say that 99.9% of the time, it's the readers perceptions that end up conveying the wrong the message or distorting the writer's words. And thus the writer's true intention is lost.
As a result, I must be mindful of what I write and how I present that written word. I must be mindful of it's tone and take into consideration the perception of others who have not had my particular experiences.
For a writer, this can be quite the challenging task.