E have met several authors in the book of Psalms so far: David, Asaph, Heman... and now, Ethan. Ethan has much to say in Psalm 89 about how wonderful and admirable Jehovah really is. There are also a number of verses here that apply variously to David and to the Messiah.
So, what is the message of Psalm 89? Worship God! He is merciful. He is faithful. He is the Creator. He has made great and precious promises to His people and to their king. He is unique. He is strong. He is holy and good. He defends His people. He executes justice against transgressors. God is worthy to be praised! In short, those of us who know Him are blessed indeed (Psalm 89:15).
However, sometimes God's wonderful and attractive characteristics can be temporarily eclipsed to our mind by the difficulties of life and by His willingness to delay the fulfillment of His words. To us it may seem (at times) that time means nothing to God. Perhaps that's not as far from the truth as we might imagine either (Psalm 89:46-47). Especially when we look at life only through our own eyes, we may suspect that God has hidden Himself somewhere and isn't active. Of course, God's ways are perfect. We must have faith that every promise God has ever made, He will keep (Hebrews 6:18 & Titus 1:2).