Psalm 89:15

Blessed is the people that know the joyful sound: they shall walk, Oh Lord, in the light of thy countenance.

Praise of the Lord helps us focus on the goodness and the light that God brings into our lives.  When we are thankful for something, we express our appreciation, and our spirits lift.  Praise lifts our spirits and moves us closer to God so we can walk in the light of His countenance.