"A whip is for the horse, a bridle for the donkey, and a rod for the back of fools"
The focus of this proverb is what brings about controlled positive behavior. The measures used with a horse, the measures used with a donkey, and the measures used with a fool are all harsh, constant, and demanding.
The clear teaching is that if a person is selfish, impulsive, and rebellious then constant, demanding, and even harsh constraints are the only way to bring out of the fool a positive and lasting set of behaviors. There is no easy way to deal with a person who has no self-discipline. This proverb is trying to cut away the sugarcoating and give the honest truth about dealing with a fool – as a son or daughter, as an employee, as a constituent, as anyone who is rightfully under your care and over whom you exercise oversight and direction.
Being upset with their behavior will not change their life; they need firm and even harsh, demanding, and constant direction to hopefully develop internal self-discipline over time. Some people, however, will never be self-motivated and need constant direction and boundaries.
The direction of this proverb is very difficult for our present culture to hear. Our culture has elevated choice and self-determination to the place of highest value. We can't tell or force anyone to do anything they don't want to do. We want to let everyone do what they want to do. This is, however, moral nonsense. Everyone cannot do what they want to do. Many times they have to do what is right even when they don't want to. This is the most difficult assignment for the fool. The fool has been on a constant journey of doing whatever he/she wants to do.
In order to build a great family, a great company, a great church, or a great community, everyone will have to do things that they don't want to do at times. Some people who are not given to restricting their own selfish impulses will need closer supervision and controls lest they detour into their own selfish ways again. It is important to help, supervise, direct, coach, and even control someone into doing the right thing.
This proverb is about the need for strong unbending controls to guide the fool back to a productive road. Realize that this is the role of the leader. Leadership is hard because you have to get people to sublimate their personal desires for the good of the team.
This would also imply that when you find an area of foolishness in your own life, that you not coddle yourself. Instead, you should be demanding, constant, and harsh for if there is a way for you to be selfish, impulsive, and rebellious in this area, then you will. And that tendency will move you away from the positive activities that you could be engaged in and send you down the path that leads to further trouble.