There might be a man or a woman that God has used in your life, perhaps a pastor, a teacher, a parent, or a friend who has had a dramatic influence on you. Then one day, you discovered they were human, and yes, that they even make mistakes. You were devastated. Maybe you thought, "If a person like that would make a mistake, then I'm not going to be a Christian."
But let me ask you: who are you following? If you are ready to abandon your faith because someone you respected slipped up, that would suggest to me that you are not worshiping the Lord, but instead have made a god out of a person. Other people can be a good influence on us, but they will fail now and then, because all of us will fail at one time or another.
We can also make a god out of tradition. When the Israelites were rebelling against God, He judged them by sending venomous serpents into their midst. Then He instructed Moses to make a serpent out of bronze and put it up on a pole. Those who had been bitten by the serpents saw it and were healed. But years later, they ended up worshiping that image of the snake wrapped around the pole, and King Hezekiah had to destroy it (see 2 Kings 18:4). Something that had been legitimately used of God became an idol.
Sometimes we think only bad things can become idols. But idols can be things that are good, but that we put in an improper place in our lives. You can make a good thing into an idol that can eventually get in the way of the Lord. That is why we need to be careful.