The Sacraments are "signs and testimonies of God's will toward us." (AC XIII) Perhaps the difficulty of understanding the sacraments comes from the way we, as sinful people, tend to divide them from God's Word and faith.
The Sacraments do not exist apart from God's Word. It is not as if there could be the possibility of Baptism or the Lord's Supper without the Word of God. Through His Word of promise God declares that we are united to Christ in baptism, that Jesus is truly (physically) present in the Supper. The Word makes the Sacrament.
It is also false to say that we can reap the benefits of a sacrament without faith. In fact, Paul says just the opposite. Sacraments received without faith are detrimental to our salvation. (I Corinthians 11:27-32)
That, however, is precisely because the Sacrament is powerful without our faith. If the sacrament required faith in order to be powerful then it could not hurt those without faith. But it does (harm). So it is (powerful).
A sacrament is an objective time and place where God declares with His Word, using the visible marker of the Water or Bread and Wine, that the death and resurrection of Jesus Christ is FOR YOU! It has come to bear upon your life.
In this way the sacraments (God's Word in visible form) sustain faith, and (in the case of baptism) even create it where it does not exist.
[Tomorrow: We stand for Rightly Called Ministers!]