Love this quote. Why is it so difficult? Because we have so many words at our disposal. Words have so many nuances, depths and shades of meaning, connotations and denotations, all of which can or may be influenced by context and subject to interpretation by a reader according to their life experiences and even their sense of humour.
Another reason is because there are so many ways in which to use the words we have, so many ways to tell the same story. The same basic story told by different writers, or even the same writer at a different time in their life, can give a reader vastly different experiences.
Luckily, we are not confined to the first draft of our story. There is always room for improvement. The danger being that at some point we have to stop polishing the story and actually send that story out into the big wide world.