Personally, the hardest task for me is to create language that wasn't said before to describe things in new and insightful ways. (aka, Virginia Woolf's commentary on Words)
Creating figures of speech, etc, is hard.
1. All writers are involved, in some way or another, in thinking of new (to them) figures of speech. An example, from Ciaran Carson, about music, is that lyrical music is like a celluloid ball on a jet of water.
Language is a funny thing. I haven't studied it thoroughly, but from my limited knowledge and experience, older versions of languages are very literary, full of metaphors, similes, and turns of phrases that have now been shortened and cropped into single words. While this is more useful and efficient, it makes it harder to think poetically. On the other hand, our lack of poetic language is what gives poetry value beyond everyday speech.
2. The process of language begins, organically ( like the succession of plants in an area that moves from stream or rock or dirt to flower and grass and meadow tree to forest ) with figs of speech and what we now call poetry to describe things that do not yet exist, then proceeds to the creation of efficient words.
If this is the case, then we can continue to move on in our understanding of language to make a few conclusions.
To be a writer is to engage in the creation of language. To be a creative writer is to be there at its base, at its beginning. While people who coin a word might be considered the creators of language, but the people who create the poetic descriptions, whether they stick or not, are there, at the microscopic interplay of simple beauty, flowering interactions, the bustling beginnings of the ecosystem of language.
Words are complex. They must be learned. Terms are smaller, like icebergs on the ocean. They seem small, but their base is the underwater etymology, the bacteria, the minerals, the veins and cracks, blue and green and rusty, coloring and supporting the weight of the term that seems to sit on the surface.
To be a writer is partly to strip off the layers, shave away the top, until you get to the core, and regain, unlearn the sophistication of terminology, and reach that colorful land teeming with poetry.
Or, of course,
This could just be the random musing of someone who's read too much theory
In the end, it's much more useful just to think about what works, what sounds good, what you like to read, etc. At least, if you want to actually write anything.