This Psalm ends Book 3 of the Psalms- Psalms 73-89
It is unique in that it moves from praise in vs. 1-18 to lament in vs. 38-52. Most psalms of lament move in the opposite direction- Pss. 13, 22, 31, 69 are examples. 

Lovingkindness- NASB or steadfast love- ESV is a key word in the Psalm appearing in vs. 1, 2, 14, 24, 28, 33, 49.

Faithfulness is also found 7 times in the Psalm- vs. 1, 2, 5, 8, 24, 33, 49.

The word forever appears in vs. 1, 2, 4, 28, 29, 36, 37

God's lovingkindess and faithfulness are forever displayed in His covenant with David. 

89:5-7 Even though people feared death when they saw an angel- Gen. 16:13; 32:3; Exodus 24:9-11; Judges 6:22-24; 13:19-22- the angels are overwhelmed with the presence of God

89:8-10 He is incomparable and He rules the seas- Ps. 65:7; 107:29

89:14 His throne is built on righteousness and justice and lovingkindness and faithfulness are fundamental to who He is