Think about the word critic for a moment. What comes into your mind? Crid - ick! So if your inner art critic starts jabbering away while you are trying to get some artwork done, just say outloud, "You are a crid-ick! Go away I am trying to get some painting done here."
If you want a more mature method of dealing with your critic affecting your ability to create art, try focusing on the process of creating but try not to judge what you are creating. Either way, lets banish those criD-icks.