Two things tend to happen when the Inner Critic has been lying low: either you keep being happy, or you start looking for it to invite back in. Or of course, the Inner Critic reappears, seemingly without your invitation at all.
Imagine dealing with a vampire who has stepped into your house. Either you can scream and try to run, so tense that you’re practically guaranteed to get caught; or you can keep doing whatever you were doing, maybe brushing your teeth, and casually wave some garlic at it.
In other words, if you find yourself dealing with the Inner Critic again, the more you treat it as a powerful threat, the more powerful it will be.
(The New York Times has an article about the imp of the perverse… and how the more you try not to think of something, the more you think of it.
http://www.nytimes.com/2009/07/07/health/07mind.html?th&emc=th)
Instead, greet the Inner Critic with “Oh, you again. Whatever.” and get on with your business. Don’t bother trying to shut it up; just don’t listen to it.