Hebrews 10, concerns people who are committing a specific sin.
Hebrews 10 concerns a specific sin these people described here are committing . . . . deliberately . . . . . AND continuing to commit that sin deliberately.
They are obstinate in this sin (they don’t repent–ever). They choose by their own volition to reject God’s grace and KEEP rejecting God’s grace.
It is not talking about people who commit this sin, then DO repent.
What specific sin is the author of Hebrews talking about?
Apostatizing–rejecting the Mass. Not “meeting together as is the habit of some” for the Eucharistic assembly. See here for more details.
The same type of situation is seen with Hebrews 6:4-6.
The Ignatius Catholic Study Bible New Testament (p. 423) says:
6:6 commit apostasy: The Greek verb means “to fall away” in the sense of failing to make good on a commitment. . . .
In other words, they fall away and keep falling away. They persist in this falling away (failing to make good on a commitment). They commit apostasy and remain in that sin (they freely choose to be obstinate in their serious sin).
That’s who these verses are talking about (obstinate sinners who are in apostasy).
They reject grace (including the grace of repentance) in this life and thus “already judge(s) oneself”.
CCC 679 Christ is Lord of eternal life. Full right to pass definitive judgment on the works and hearts of men belongs to him as redeemer of the world. He “acquired” this right by his cross. The Father has given “all judgment to the Son”.587 Yet the Son did not come to judge, but to save and to give the life he has in himself.588 By rejecting grace in this life, one already judges oneself, receives according to one’s works, and can even condemn oneself for all eternity by rejecting the Spirit of love.589
Footnote 589 here in the CCC cites among other things, Hebrews 6:4-6 and Hebrews 10:26-31. Bold CCC mine.
This doesn’t mean the people referred to here in Hebrews chapters 6 and 10, don’t have the gifts and graces of a repentance offered to them (remember even repentance is a gift and grace from God–see 2nd Timothy 2:25-26).
It also doesn’t mean that EVERYBODY who commits apostasy remains unrepentant.
These verses are just talking about the ones who DO (remain unrepentant).
These verses concern they who commit apostasy and choose to reject the grace of repentance, and choose to continue to reject it of their own free will.
The continuing action in the Greek is apparently lost in the translation. I bolded and underlined the phrases for you and added parenthesis below that show this is not only a sin, but a persistence in this sin.
HEBREWS 6:4-6 4 For it is impossible to restore again to repentance those who have once been enlightened, who have tasted the heavenly gift, and have become partakers of the Holy Spirit, 5 and have tasted the goodness of the word of God and the powers of the age to come, 6 if they then commit (and keep committing) apostasy, since they crucify the Son of God on their own account and hold him up to contempt.
HEBREWS 10:24-27, 29b, 38-39 24 and let us consider how to stir up one another to love and good works, 25 not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near. 26 For if we sin deliberately (and keep persisting in this sin deliberately) after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a fearful prospect of judgment, and a fury of fire which will consume the adversaries. . . . the man who has spurned the Son of God, and profaned the blood of the covenant by which he was sanctified, and outraged the Spirit of grace? . . . 38 but my righteous one shall live by faith, and if he shrinks back, my soul has no pleasure in him." 39 But we are not of those who shrink back and are destroyed, but of those who have faith and keep their souls.
So as Hebrews 10:23a says: " Let us hold fast the confession of our hope without wavering".