1 Samuel 10:9 And it was so, that when he had turned his back to go from Samuel, God gave him another heart: and all those signs came to pass that day.
God Gave Saul Another Heart
Saul started out right as a king. God gave him another heart. Maybe his heart was not right at the time or it was weak or doubting or some other defect, but in the end, God made up the difference and helped Saul to be a good king. The problem was he had a bad heart and God needed to fix it if he was going to be a king. It says in Psalms the the heart of the king is in the hand of the Lord. The Lord needs to have control over the rulers of this world to accomplish His will in our lives. Saul had a good heart for many years. A lot of people start out good.
A Bad Heart Later in Life
The problem came when jealousy and envy and pride came into play. His first problem was he did not trust the man of God. He was not willing to wait on Samuel to come make the sacrifice. He forced himself to do what God had reserved for the priests. It sounds like he got his old heart back. This seems to happen with a lot of Christians. They go back to the world. Their old heart came back overtook the new heart. The new heart God gave them was not good enough. They let the flesh finally win out. Saul could not overcome that old man. It got him in the end. It drove him insane. All he wanted toward the end was just to kill David. We need to constantly keep our heart right with God or in the end we could end up like Saul with a destroyed life.