(Thanks to Elder Delange for this idea, one of the funniest and most humble missionaries I had the privilege of serving with.)
Inside everyone's head is a republic. The republic is body of representatives, a quorum, so to speak, of each and every feeling and thought process a person has. Each representative is dressed appropriate to the feelings they represent, and all of them meet in your head and vote on what you want to say and do.
There's a wisdom faction that makes sure you stay on the course. There's a safety faction to make sure that when you're lighting off bottle rockets for the 4th you don't burn your face off. There's a whiny faction that makes you go home and blame your bad day on everyone else but you. There's a hungry faction, a tired faction, a comedic faction, and so on ad infinitum. The human brain is a fabulous specimen of the Almighty's handiwork.
They all meet in a great hall, lavishly decorated, filled with plush seats. The room is acoustically sound; the smallest faction has the same voice as the largest. When you have an idea, it is presented as a bill. Each bill is voted upon, and when ratified, you say/do/eat/watch/think/shout/procrastinate something. When the bill is vetoed, you either forget about it or the faction that presented it waits for a later time, politicks around to gain support, and puts the bill up for ratification at a later time. (This is why diets rarely stick.)
Most republics conduct themselves in an orderly fashion. Mine on the other hand...
I have a large contingent of impulsive monkeys each equipped with a green stamp. I always regret what I say. *sigh*