King Saul thought highly of himself, but that did not matter, for what the Lord thinks of us is what matters. Saul had already been disobedient to the Lord. Therefore, on a new occasion, Saul believed that he had obeyed the Lord, and so the king set up a monument for himself, and proclaimed his obedience,

So when Samuel rose early in the morning to meet Saul, it was told Samuel, saying, “Saul went to Carmel, and indeed, he set up a monument for himself; and he has gone on around, passed by, and gone down to Gilgal.” Then Samuel went to Saul, and Saul said to him, “Blessed are you of the Lord! I have performed the commandment of the Lord.” But Samuel said, “What then is this bleating of the sheep in my ears, and the lowing of the oxen which I hear?” (1 Samuel 15.12–14).

Look at Saul. He set up a monument for himself, he excitedly blessed Samuel, and Saul boasted of doing what the Lord said to do.

Samuel only needed to ask one question, Why do I hear the sound of these animals? Meaning that Saul had not destroyed everything associated with the Amalekites, and thus not obeyed the Lord, and had no reason for setting up monuments for himself.

Therefore, let us not be consumed with our self-opinions, but let us be consumed with doing as the Lord says, and let Him exalt us or humble us, as needed.