Thomas Merton, New Seeds of Contemplation:
If you write for God you will reach many people and bring them joy.
If you write for people you may make some money and you may give someone a little joy and you may make a noise in the world, for a little while.
If you write only for yourself you can read what you yourself have written and after ten minutes you will be so disgusted you will wish that you were dead.
Better to write for God then…!