Psa 103:1 A Psalm of David. Bless the LORD, O my soul, and all that is within me, bless his holy name!
Bless the Lord, O my soul is a conscious decision a believer makes to acknowledge and bless God for who He is. This praise does not stem for what He has done but for the being He is. David repeats this in vs 2; also at the end of the psalm; and again in Psa 104:1, Psa 104:35. To “bless” is more than to praise, it is to praise with affection and gratitude. Consider these words from Moses as he blesses the Lord Deu 32:3-4, “3 For I proclaim the name of the LORD: Ascribe greatness to our God. 4 He is the Rock, His work is perfect; For all His ways are justice, A God of truth and without injustice; Righteous and upright is He.” This has little to do with how we feel. As with the psalmist, he calls upon his own soul, an encouragement to his weary soul to begin the song of praise, which is to translate in a general chorus of blessing from all creation (Psa 104:20-22).
And all that is within me. All my whole nature—intellect, emotion, feeling, brain, heart, lungs, tongue etc. to bless His holy Name, that is His manifested Personality, the Personhood of God, which is almost the same thing as Himself. Let every part of our being that has life bless the Lord.