God will listen to me.
The author no longer doubts, as in Psalm 55:1–2. “He will humble them. He, the King of old, sits on the throne. It is clear that God will deal with them, and there is ample reason for that. After all, they do not change. They do not repent.
So, their enmity continues. They do not fear God. While he is the eternal King.
The author already talked about dealing with the enemy (Psalm 55:9–11) in Psalm 55:9 and Psalm 55:15. Perhaps there is a link with 2 Samuel 16:5—already referenced in the comments by Psalm 55:14. We see Shimei from the tribe of Benjamin, to which Saul also belonged; he continually curses David, who is being chased by Absalom. Abishai wants David to deal with this cursing Shimei. But David does not do that; he points to the Lord. We read this in 2 Samuel 16:12: “It may be that the Lord will look on the wrong done to me, and that the Lord will repay me with good for his cursing today.” David shows reverent awe for the Lord. We see here the shadow of the Saviour: justice of God.
19 God will give ear and humble them, he who is enthroned from of old, Selah because they do not change and do not fear God.