We are like a rider on top of a gigantic elephant. We can steer the elephant, and if he's not busy, he'll go where we want, but if he has other desires, he'll often go where he wants. How can one control the elephant? In part, this comes with maturity. In part, this comes with the development of your frontal cortex, so the frontal areas of the brain are especially involved in self-control, in suppressing your initial instinct to act. This is why teenagers are so impulsive. So it's terrible to allow the death penalty for teenagers, because they really don't have working brains yet.