Verbal expressions of one’s own love for God have no biblical warrant. No one in the First Testament ever tells God, “I love you.” Appeals to love God are common (Deut 6:5), but no authors or characters have the audacity to claim that they measure up to the standard demanded by the word.* In any case, love is demonstrated in actions, and only God may judge whether these actions demonstrate true covenant love. The picture does not change in the New Testament.
(…) Ultimately, we do not praise God by telling him we will praise him anymore than we prove we love God by telling him that we do love him. Apart from actually recounting his glorious acts of creation and providence and his gracious acts of salvation, these are empty promises.
— Daniel Block, ‘For the Glory of God’
*(Block explains how Psalm 18:1 and 116:1 are not exceptions — in the former, the psalmist creates an awkward sentence so as to not directly tell God he loves him; in the latter, the psalmist says, “I love… because YHWH”, leaving out an object of his love.)