So I've been reading through the Psalms and I noticed a few things. In Psalm 107 there was four different scenarios (hunger and thirst, difficult work, death, fright/shipwreck). In each of those scenarios, the Lord delivers them and then it says (each time): Oh, that these men would praise the Lord for his lovingkindness and for all His wonderful deeds.
Then at the beginning of Psalm 118 it says, let them praise the Lord with these words: His lovingkindness is forever.
And in Psalm 136 at the end of each of the 26 verses, it says: for His lovingkindness continues forever.