The good writer/artist/preacher disappears in his work, but that does not mean that he is not revealing himself:
Writing is revealing yourself, not concealing yourself. Revealing yourself does not necessarily mean exhibiting yourself. Revelation and exhibitionism may be the same thing, but not inevitably. If you conceal yourself, you are no writer. You may be a banker, a general, certainly a statesman—but not a writer. Writing need not be an unabashed revelation of the emotions, but when you write you express, even through other characters, what you are and who you are. You cannot repress and express—they are contradictory terms.
In everything you write there are two more characters than you think. There’s yourself, and there is your audience.
-Samson Raphaelson, The Human Nature of Playwriting, Kindle loc. 480, 1946
Everything you write is autobiographical. You are always a character. You cannot not work from your own experience and personality. The trick is that you should be on a mission of revelation, not exhibition.
The good preacher (and writer) reveals his heart, but never puts himself on exhibit. In the words of Spurgeon, his own chains clank as he preaches to himself, but the listeners won’t always discern the sound. They’ll think it is their chains clanking, and that he is actually preaching to them.