Himself.

Try, like some first human being, to say what you see and experience and love and lose. Do not write love-poems; avoid at first those forms that are too facile and commonplace: they are the most difficult, for it takes a great, fully matured power to give something of your own where good and even excellent traditions come to mind in quantity. Therefore save yourself from these general themes and seek those which your own everyday life offers you; describe your sorrows and desires, passing thoughts and the belief in some sort of beauty — describe all these with loving, quiet, humble sincerity, and use, to express yourself, the things in your environment, the images from your dreams, and the objects of your memory. If your daily life seems poor, do not blame it; blame yourself, tell yourself that you are not poet enough to call forth its riches; for to the creator there is no poverty and no poor indifferent place.

I know no advice for you save this: to go into yourself and test the deeps in which your life takes rise; at its source you will find the answer to the question whether you must create. Accept it, just as it sounds, without inquiring into it. Perhaps it will turn out that you are called to be an artist. Then take that destiny upon yourself and bear it, its burden and its greatness, without ever asking what recompense might come from outside. For the creator must be a world for himself and find everything in himself and in Nature to whom he has attached himself.

Rainer Maria Rilke, from Letters to a Young Poet