Praise the Lord,' is the phrase with which the last five psalms of the Psalter begins. Worship involves confession of our sins. Much OT worship makes that clear. A broken and a contrite heart, O God, thou dost not despise. Ps.51, and Isaiah's vision of the Lord, and Peter seeing the nets breaking under the weight of the fish and crying, 'Depart from me.
Worship involves thankfulness and joy.
A tremendous number of the psalms reflect this. One Easter Sunday morning GM was preaching on the resurrection in a church in Glasgow. He notices a man who was listening intently to every word of the sermon. He was the sort of listener that you want every member of the congregation to be like. After the service GM went on to him and asked if he were a member of this congregation.