What a promise from the Lord! What made it even more amazing was Jeroboam had no claim to royalty. By anyone's standard he was an average Joe. What made him special was he was chosen by God. It's amazing to me how a man like this is given everything, and yet, blows it. He began to think in his own flesh and leave the leading of the Spirit of God. Subsequently, it wasn't long until Jeroboam forgot about God. He began to take matters in his own hands and make decisions based on his fears and lack of faith.
We move ahead to chapter 14 where we see Jeroboam in a family crisis. His son has fallen ill and they fear for his life. Moving along we see Jeroboam's son dying and his kingship being taken. He loses everything. Why? Because he sought the advice of man instead of God.
Look back to chapter 12. When Jeroboam became king, he was faced with a dilemma. God's temple was located in an area where his adversaries lived. Remember, two of the twelve tribes refused to recognize him as king. God's temple was located in Jerusalem, his rival's turf. What makes this story all the more interesting is God himself made it very clear they could not worship anywhere they pleased...it had to be in Jerusalem.
1 Kings 12:26 Jeroboam thought to himself, "The kingdom will now likely revert to the house of David. If these people go up to offer sacrifices at the temple of the LORD in Jerusalem, they will again give their allegiance to their Lord, Rehoboam king of Judah. They will kill me and return to King Rehoboam." After seeking advice, the king made two golden calves. He said to the people, "It is too much for you to go up to Jerusalem. Here are your gods, O Israel, who brought you up out of Egypt." One he set up in Bethel, and the other in Dan. And this thing became a sin; the people went even as far as Dan to worship the one there.