Bradley Johnston, in his book "150 Questions about the Psalter", insightfully expands on this question:
“Where does the Psalter move our attention as we sing?”
The Psalter moves our attention in a variety of directions as we sing.
It teaches us to focus upon the triune God and his mighty works, to ponder the condition of our own hearts and our affections, to consider the character of God’s people gathered in worship, to behold the nations in their rebellious unbelief, and above all, to cherish the good and sovereign reign of the messianic King. (p 51)
We know intuitively that we generally have a lot on our minds during each day. Nonetheless, in the singing of the psalms our attention is spiritually refocused on these wonderful realities that we are participants in!
Lift your voices and be renewed in your hearts and minds through the praise of His Holy Name!