The Bible talks a lot about sheep, and it mentions the fact that we are just like sheep ourselves. It also says, "All we like sheep have gone astray; we have turned, every one, to his own way . . ." (Isaiah 53:6). The thing with sheep is they need shepherds around them at all times, guiding them and guarding them and helping them.
One of the most well-known passages in the Bible about sheep is Psalm 23, written by David, a shepherd. It begins, "The Lord is my shepherd; I shall not want. He makes me to lie down in green pastures; He leads me beside the still waters. He restores my soul. . . ."
Sheep have to be told when it is time to eat. Then they have to be told when it is time to lie down and when to drink some water. They have no way to defend themselves. They need the shepherd to protect them, just like we need our Shepherd to protect us as well.
But David goes on to say, "Yea, though I walk through the valley of the shadow of death, I will fear no evil; for You are with me; Your rod and Your staff, they comfort me" (verse 4).
A shepherd would use a staff to keep the sheep where they were supposed to be and to guide them. In the same way, sometimes when we go astray, God has to use a staff to bring us back again.
If the staff doesn't work, however, there is another instrument the shepherd would carry, and that is a rod, which is basically a club. A shepherd would use the club when the situation was serious.
Sometimes God will use a staff in our lives. But sometimes God will have to use the rod.