What does Psalm 118:28 mean?

Here, the psalm turns to direct expressions of praise to the Lord. He is referred to as "my God," using two different Hebrew words. The first is ēl', which literally refers to power and is often used regarding deities. The second is elōhim, a plural term referring to "gods" but often used to refer to the One True God (Genesis 1:1; Exodus 7:16; Leviticus 11:44; Deuteronomy 6:4). Both appear in English as "God," but carry a subtly different emphasis.

The statements here are personal. The psalmist sees the Lord as his Lord, not merely "a" Lord or power. This relationship only comes through truly saving faith. It is not passed down through heritage (John 8:33, 39, 41). Those who find this salvation have the ultimate reason to be grateful and to give thanks (Ephesians 5:20; Colossians 3:17)

To "extol" or "exalt" means to speak of in a positive way: improving the subject's reputation and standing in the eyes of other people.