I have learned that being thankful (even for things I don't care much about) adds to my mental health. I think that is the way God designed us because He tells us to 'always be thankful'.
Here are the lead-in lines to the last five chapters of Psalms:
"Praise the Lord! Yes, really praise Him!" (Psalm 146)
"Hallelujah! Yes, praise the Lord! How good it is to sing His praises! How delightful, and how right!" (Psalm 147)
"Praise the Lord, O heavens! Praise Him from the skies!" (Psalm 148)
"Hallelujah! Yes, praise the Lord! Sing Him a new song. Sing His praises, all His people." (Psalm 149)
"Hallelujah! Yes, praise the Lord! Praise Him in His Temple, and in the heavens He made with mighty power." (Psalm 150)
Bible Commentary: "These last five psalms overflow with praise. Each begins with "Hallelujah" or "praise the Lord". They show us where, why, and how to praise God. What does praise do?
~ Praise takes our minds of our problems and shortcomings, and focuses them on God;
~ Praise takes us from individual meditation to corporate worship;
~ Praise causes us to consider and appreciate God's character;
~ Praise takes our perspective from the earthly to the heavenly."