We put a bit, a small metal bar, in the mouth of a horse to make it obey us, and we can control the whole animal with it.
If someone thinks they’re religious, but they don’t control what they say, then they’re fooling themselves and their religion isn’t worth anything.
To give another example, ships are very big, and they’re driven along by strong winds. But they can be steered by a very small rudder that makes them go wherever the captain wants to go.