The psalmist David, on many occasions, told His soul to bless the Lord.  He was telling His will, mind and emotions to show adoration to the Almighty God. 
“Bless the Lord, O my soul; And all that is within me, bless His holy name! Bless the Lord, O my soul” Psalm 103:1-2
In other words, he was telling his soul to get its act together.  In Hebrew, “to bless” is the word barak, and it also means “knee.”   So how do we bless God?  We are to bow down before God and worship Him.   And in turn, we will be blessed.   
God blesses us to be a blessing to others.  
Let us do what we sing every Christmas: “Come, come let us adore Him,
kneel down before Him, worship and adore Him.”