Dear Leon:

The best one-liner definition of a Sacrament was given during a homily by the priest who received me into full communion into the Church. He said, "A Sacrament is an physical manifestion of an invisible reality."

For example, the love between a man and woman is invisible, but we bring that love into a physical manifestation called the Sacrament of Marriage.

In the Sacrament of Baptism, the new birth of the person and the indwelling of the Holy Spirit is invisible, but made manifest by the Sacraments of Baptism and Confirmation.

The Sacrament of the Eucharist is also a physical manifestation of the invisible reality of the of the Body and Blood of our Lord in the Eucharist and in heaven.

The Sacraments are dim images of the reality behind them.

St. Paul tells us, (1 Cor 13:12)  "For now we see in a mirror dimly, but then face to face. Now I know in part; then I shall understand fully, even as I have been fully understood." 

The Catechism states, quoting from Scripture (Luke 22:19): 

1341 The command of Jesus to repeat his actions and words "until he comes" does not only ask us to remember Jesus and what he did. It is directed at the liturgical celebration, by the apostles and their successors, of the memorial of Christ, of his life, of his death, of his Resurrection, and of his intercession in the presence of the Father.

(Luke 22:19)  And he took bread, and when he had given thanks he broke it and gave it to them, saying, "This is my body which is given for you. Do this in remembrance of me." 

In heaven all is revealed, we will see things clearly for what they are. The invisible reality will no longer be invisible. Thus, the Sacraments, which are ordered to our earthly existence, are not needed in heaven. We will not have to "remember" Jesus because we will see him personally face-to-face in heaven.

In addition, Jesus told us to remember him in the Eucharist "until he comes". That means, until the Second Coming of Christ, when all things invisible will be made manifest.

God Bless,
Bro. Ignatius Mary