But you do not deny that "by the grace of God" one can merit eternal life, becoming good enough to be with God?
The growing in holiness prepares us for our eternity in the presence of God. In the presence of God there can be no evil, no "stain" - we progress towards godliness in preparing ourselves for Him. It does not save us, we do nothing to save ourselves.
Just where do you get this "it does not save us, we do nothing to save ourselves" from Catholic teaching, which teaches that one is justified by the good works that he performs by the grace of God, and is accounted to have truly merited eternal life by these very works he did in God (meriting salvation by grace). (Trent, Chapter XVI; The Sixth Session Decree on justification; Canon 32)
And that being initially formally justified and made holy by his own personal justice and holiness (causa formalis) means that one must actually become good enough in character to be with God via the purifying punishments of RC Purgatory, unless he has attained to that state by the time (and maintains to the time) he dies?
By making "grace" as the cause of salvation by works the Catholic attempts to avoid the charge, but which basically makes salvation as being under the law, requiring practical perfection in order to be with God.
Believers are accounted to be believers and fit to be rewarded in the light of the evidence of their faith, (Mt. 25:31-40; Rv. 3:2) which God rewards, (Heb. 10:35) but the basis for their acceptance with God is by heart-purifying regenerating faith (Acts 10:43; 15:7-9) being counted for righteousness, (Rm. 4:5) the sinner being made accepted in the Beloved, and made to positionally sit together with Him in Heaven, on His account, (Eph. 1:6;2:6) by whose sinless shed blood he has direct access with boldness into the holy of holies in Heaven, (Heb. 10:19) even though he yet possesses the defiled carnal nature in which dwelleth no good thing, (Rm. 7:18) but which shall not be with him after death, in which he ceases to sin. (Rm. 6:7)
Expresses more fully, purgatory is based upon a false premise, that of the need for perfection of character (if by grace) in order to be with God, versus penitent faith which appropriates justification, which purifies the heart (Acts 15:9) and is counted for righteousness (Romans 4:5) and renders one accepted in the Beloved (on His account) and positionally seated together with their Lord in Heaven, (Ephesians 1:6; 2:6) from where they await the Lord's return and His final subduing of our "vile body," that it may be fashioned like unto his glorious body," (Philippians 3:21)and which is the only transformative change after this life that the Scriptures speak of.
However, this saving justifying faith, is a faith which effects obedience by the Spirit, in word and in deed, in heart and in life, whereby "the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit, (Romans 8:4) insofar as we do. And since faith and works go together like light and heat, sometimes they are used interchangeably as to what they effect. And which obedience includes penitent confession when convicted of not pleasing the Object of his faith for salvation, the risen Lord Jesus.
The appeal to the believer is to produce fruit consistent with faith, as a consequence of being accepted in the Beloved (on His account), to be practically (in heart and deed) as they are positionally in Christ, to be as much conformed to the Lord Jesus in this life as we can be, and will be in the resurrection. (Philippians 3:7-21) If we live in the Spirit, let us also walk in the Spirit. (Galatians 5:25)
If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God. Set your affection on things above, not on things on the earth. For ye are dead, and your life is hid with Christ in God. When Christ, who is our life, shall appear, then shall ye also appear with him in glory. (Colossians 3:1-4)
But which progressive practical sanctification is not the cause of the sinner's justification and acceptance in Christ, but testifies to such being a believer, evidencing "things which accompany salvation," (Hebrews 6:9) and fit to be rewarded. (Revelation 3:4) For this faith, as manifested in said obedience, God will recompense (Hebrews 10:35) under grace, even though it is God who motivates and enables all obedience, (Philippians 1:12,13) while the only thing we can and must take credit for it our disobedience.
In contrast to this salvation by effectual faith, is salvation by grace thru works, as in Roman Catholicism, in which by grace one is actually made good enough to be with God via the act of baptism, even without the required wholehearted repentant faith. (Acts 8:38; 8:36,37)
However, since the carnal nature remains and few successfully attain to complete victory over any attachment to sin and perfection of character, then most baptized souls are sent to Roman Catholic (EOs trend to reject Rome's) Purgatory to endure purifying torments to atone for sins they sufficiently failed to provide for while on earth, and become good enough to enter glory.
There is some wiggle room as regards the conditions of purgatory since what this suffering actually entails and how long are not dogmatically taught, but while salvation by grace thru faith as in sola fide means it is effectual faith being imputed for righteousness that justifies, salvation by grace thru works means that by grace one is actually made good enough to be with God, which premise either requires perfection of character in this life (and which merely being made clean in baptism would actually not effect) or postmortem purifying torments.
The Catholic Encyclopedia states that St. Augustine "describes two conditions of men; "some there are who have departed this life, not so bad as to be deemed unworthy of mercy, nor so good as to be entitled to immediate happiness" etc.
And thus by the close of the fourth century was taught "a place of purgation..from which when purified they "were admitted unto the Holy Mount of the Lord". For " they were "not so good as to be entitled to eternal happiness". - CATHOLIC ENCYCLOPEDIA: Purgatory
Likewise Catholic professor Peter Kreeft states,
"...we will go to Purgatory first, and then to Heaven after we are purged of all selfishness and bad habits and character faults." Peter Kreeft, Because God Is Real: Sixteen Questions, One Answer, p. 224
However, wherever Scripture clearly speak of the next conscious reality for believers then it is with the Lord, (Lk. 23:43 [cf. 2Cor. 12:4; Rv. 2:7]; Phil 1:23; 2Cor. 5:8 [“we”]; 1Cor. 15:51ff'; 1Thess. 4:17) Note in the latter case all believers were assured that if the Lord returned, which they expected in their lifetime, so would they “ever be with the Lord,” though they were still undergoing growth in grace, as was Paul. (Phil. 3:7f)
And the next transformative experience that is manifestly taught is that of being like Christ in the resurrection. (1Jn. 3:2; Rm. 8:23; 1Co 15:53,54; 2Co. 2-4) At which time is the judgment seat of Christ, which is the only suffering after this life, which does not begin at death, but awaits the Lord's return, (1 Corinthians 4:5; 2 Timothy. 4:1,8; Revelation 11:18; Matthew 25:31-46; 1 Peter 1:7; 5:4) and is the suffering of the loss of rewards (and the Lord's displeasure) due to the manner of material one built the church with, which one is saved despite the loss of such, not because of. (1 Corinthians 3:8ff)
In addition, the whole premise that suffering itself perfects a person is specious, since testing of character requires being able to choose btwn alternatives, and which this world provides. Thus it is only this world that Scripture peaks of here development of character, such as "Wherein ye greatly rejoice, though now for a season, if need be, ye are in heaviness through manifold temptations." (1 Peter 1:6)
And even in making the Lord "perfect" as in experiencing testing, being "in all points tempted like as we are, yet without sin," (Hebrews 4:15) then it was in this world: "For it became him, for whom are all things, and by whom are all things, in bringing many sons unto glory, to make the captain of their salvation perfect through sufferings." (Hebrews 2:10)