Itty Bitty Snitty Committee

[Forest]

That inner voice that sabotages your thoughts or actions with self-doubt or negative reinforcement.

Example:
I was about to ask this guy out on a date when my itty bitty shitty committee told me otherwise.

See also:
http://www.urbandictionary.com/define.php?term=itty bitty shitty committee

However, we're a family friendly board here, so we try to keep it clean. Plus, I like the idea of thinking of the Committee as being in a snit. It makes it much easier for me to not take them seriously, which, after all, is the point.

A tip of the hat to Peg, who turned me on to the term.