There are two words used in our catechesis (religious instruction) that describe a vitally important aspect in the character of a religious act. If you don't know about this aspect, then you will likely misunderstand what is happening as we worship.
The first word refers to the works of man and offerings he brings to God as an act of devotion, and often in the attempt to earn God's favor or placate His wrath. That word is sacrificial. Sacrificial worship focuses upon what we, the worshippers, do. We do whatever seems best, or whatever fits best with God's law, and we consider that devotion as a partial fulfillment of our obligations toward God. That kind of worship is sacrificial in nature.
The second word is the opposite. It refers to the work of God, as He comes to the worshipper bringing and bestowing everything needed for the full forgiveness of sins, and reconciliation between God and man. We bring nothing, but encounter God, Who comes to shower His divine favor upon unworthy recipients, not because He has found any prompting in their merits, thoughts, words or deeds, but only because of His mercy and love through Jesus Christ. This is the favor Dei propter Christum, the favor of God on account of Christ.
Confessional Lutherans always have a sacramental focus in worship, rather than a sacrificial focus. Certainly, we also do some things for God, but always in response to His mercy and favor, not in an attempt to obtain them. We offer sacrifices of thanksgiving, rather than sacrifices meant to pay for our sins or satisfy the requirements of God's law.