What is the extra value of the body of Christ in the Eucharist when someone is already full of the Holy Spirit? In the Catholic Church, the Eucharist is almost the central practice of their faith. By eating the bread as the body of Christ, one is united with God, but sometimes a person can be so full of the Holy Spirit (like St. Paul) that it seems to them that the Eucharist isn't the center of their belief. 

So how did the Eucharist become the center of faith, according to the Catholic Church, if one is full of the Holy Spirit (Ephesians 1:13)? How do the Holy Spirit and the Eucharist relate to each other?
I am Catholic, and from personal experience I know that taking the Eucharist in the right conditions gives you an immediate spiritual rehabilitation.
You become more Christlike, more loving, more calm, etc.
The Church teaches that it also forgives venial sins.
What must be understood is that the Sacrifice of Christ on the cross is
the same as the eucharistic sacrifice, the Eucharist re-presents the sacrifice.
But it does not kill Jesus over and over again every time it is performed,
it's that same sacrifice on the cross which is continually re-presented in churches for the People of God.

CATHECHISM OF THE CATHOLIC CHURCH
Article 3 The Sacrement of the Eucharist
1365 Because it is the memorial of Christ's Passover, the
Eucharist is also a sacrifice. The sacrificial character of the
Eucharist is manifested in the very words of institution: &quot;This is my
body which is given for you&quot; and &quot;This cup which is poured out for you
is the New Covenant in my blood.&quot;187 In the Eucharist Christ gives us
the very body which he gave up for us on the cross, the very blood
which he &quot;poured out for many for the forgiveness of sins.&quot;188
1366 The Eucharist is thus a sacrifice because it re-presents (makes
present) the sacrifice of the cross, because it is its memorial and
because it applies its fruit:
[Christ], our Lord and God, was once and for all to offer himself to
God the Father by his death on the altar of the cross, to accomplish
there an everlasting redemption. But because his priesthood was not to
end with his death, at the Last Supper &quot;on the night when he was
betrayed,&quot; [he wanted] to leave to his beloved spouse the Church a
visible sacrifice (as the nature of man demands) by which the bloody
sacrifice which he was to accomplish once for all on the cross would
be re-presented, its memory perpetuated until the end of the world,
and its salutary power be applied to the forgiveness of the sins we
daily commit.189

Now in the case of someone who's as holy as St. Paul the Eucharist is still necessitated ordinarily.
I say ordinarily because it is possible to get a pass if you are animated by extraordinary grace like many protestants I would think.
It should also be noted that ordinary grace is more reliable, more consistent.
Of course in this case we will stick to the ordinary grace scenario.
In the Garden of Eden, Adam and Eve were kept alive because of the fruits
of the Tree of Life(Gen 3:22). In Revelation, which is the final conclusion and a miror image of Genesis, we learn that the nations are kept alive by the fruits of the Tree of Life(Rev 2:7, Rev 22:2). We know that no mere tree can keep someone alive eternally, but we also know that God likes to use physical things to usher in spiritual realities. Like the Bread and Wine of the Holy Communion.

John 6:48-50 King James Version (KJV)
I am that bread of life.
Your fathers did eat manna in the wilderness, and are dead.
This is the bread which cometh down from heaven, that a man may eat
thereof, and not die.

Taking this data into consideration, we can conclude that any ordinary ministry must be assisted by the Eucharist even if it shows saintly spiritual maturity.  The Holy Spirit is not at odds with the Eucharist, but rather cooperates with the Eucharist to &quot;decode&quot;, as it were, all the power which is hidden behind the physical apparence of the sacrifice.
Imagine the spiritual layout of your body, your body is the temple of the Holy Spirit, when you take the Eucharist you allow the Holy Spirit to fill you more, to take control of areas which were kept prisoners by habitual sins or ever demonic entities like St. Paul mentions(2 Cor 12:7-9).
This is why one must not be in mortal sin when taking the Eucharist,
it angers God and he may very well stike us dead as he could have done with Adam and Eve but instead sealed the Garden.
That is how the Eucharist became the center of the Catholic faith.
The Eucharist re-presents Christ our Lord, and it sustains us spiritually
no matter how holy one may be, in the case of ordinary ministry, we must re-fill and that's how God desired it to be. It keeps us humble and closer to him.