I got over it by stopping it. I used to write copy for catalogs like The Sharper Image. It's the biggest fraud-job in the world and it drains the writer out of you, whatever writer exists in you. "Copy" is "content" and it is basically someone else's words, not your own, coming out of "your mouth" in place of your own. It becomes a habit that you need to break before it stifles every creative impluse you have. Writers have been facing this difficulty in one fashion or another for a very long time. Look at Faulkner writing screenplays, or the myriad writers working on Madison Avenue in the 40s and 50s trying to eke out a living while attempting to produce "the Great American Novel." The same story, over and over.
And you never "post" real writing. You "publish" it. Even online.