After Shadrach, Meshach, and Abednego were rescued from the furnace and promoted, Nebuchadnezzar had a troubling dream that needed an interpretation. His magicians, the Chaldeans, and soothsayers couldn’t interpret the dream, but remembered that Daniel could. Daniel had accurately interpreted a dream Nebuchadnezzar had back in Daniel 2 without hearing the dream first so his word could be trusted.
Daniel 4:10-18 speaks of the dream Nebuchadnezzar had.
Daniel was troubled by the dream himself and wished the dream had been about one of Nebuchadnezzar's enemies. Sometimes when we realize a terrible truth, we don't want it to be about someone we're loyal to. It's too hurtful. But in the end, we must tell the truth which Daniel did.
Daniel 4:20-26 speaks of the interpretation. Basically, King Nebuchadnezzar has grown strong, but will be driven away from men. He will live among the animals and eat grass like the oxen. He will be wet with the dew of heaven and 7 times shall pass over him until he knows that God rules in the kingdom of men and gives it to whomever He chooses. The kingdom will be assured for Nebuchadnezzar after he knows that Heaven rules. Daniel encouraged Nebuchadnezzar to break off his sins by being righteous and his iniquities by showing mercy to the poor. Possibly lengthening his prosperity.
Sometimes people grow so strong and powerful in life that they forget that God was the one who allowed them to get into their positions of power. In their pride they forget Him and sometimes God must send a warning to get them back on track.