“Why or why would you want to rejct the power of the priest given in his ordination (another Sacrament).”
I don’t reject the power of the Priest, since I myself am a Priest and a King in the sight of God, as is every member of the elect (Rev 5, 1 Peter 2). I simply deny the power of carnal works to facilitate Grace, since grace is the free and unmerited gift of God.
Grace is, by definition, the unmerited favor of God on sinners. It is utterly independent of all works, which cannot add to it or take away from it without destroying its very meaning.
Rom_11:6 And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work.
One cannot “obtain” grace, since that’s the same thing as saying that you are justified by works, because your works are what succeeded in “earning” grace. But grace is always unmerited:
2Ti_1:9 Who hath saved us, and called us with an holy calling, not according to our works, but according to his own purpose and grace, which was given us in Christ Jesus before the world began,
Eph_1:4 According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
Or as Augustine says:
“We know that God’s grace is not given to all men. To those to whom it is given it is given neither according to the merits of works, nor according to the merits of the will, but by free grace. To those to whom it is not given we know that it is because of God’s righteous judgment that it is not given.”
Augustine - On Rebuke and Grace
You cannot “cooperate” with grace, because that is the same thing as saying that unmerited grace depends on you retaining your merits.
Rom_4:4 Now to him that worketh is the reward not reckoned of grace, but of debt.
Therefore grace cannot be hindered or supported by works. While the scripture teaches that we ought to work out our salvation, a sentence later it says that it is God who works in us both to will and to do:
Php 2:12-13 Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling. (13) For it is God which worketh in you both to will and to do of his good pleasure.
Php 1:6 Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:
Isa_26:12 LORD, thou wilt ordain peace for us: for thou also hast wrought all our works in us.
Salvation, therefore, is the entire work of God from start to finish. Both works and faith must bow to the will of God who chose us, not because He foresaw we would do good, but so that we would do good, as the Bishop of Hippo explained in my previous post to the other fellow.