Why not?

Help! About 70 years ago my mother read to me from the writings of Ellen White describing one of her visions where she saw those who survive the time of trouble in anguish pleading for mercy because they regard themselves as such great sinners.

From this it seems that their victory is based on mercy rather than sinless perfection.

Will someone help me find the quotation?

As Satan accuses the people of God on account of their sins, the Lord permits him to try them to the uttermost. Their confidence in God, their faith and firmness, will be severely tested. As they review the past, their hopes sink; for in their whole lives they can see little good. They are fully conscious of their weakness and unworthiness. Satan endeavors to terrify them with the thought that their cases are hopeless, that the stain of their defilement will never be washed away. He hopes so to destroy their faith that they will yield to his temptations and turn from their allegiance to God. {GC 618.3}

Though God's people will be surrounded by enemies who are bent upon their destruction, yet the anguish which they suffer is not a dread of persecution for the truth's sake; they fear that every sin has not been repented of, and that through some fault in themselves they will fail to realize the fulfillment of the Saviour's promise: I "will keep thee from the hour of temptation, which shall come upon all the world." Revelation 3:10. If they could have the assurance of pardon they would not shrink from torture or death; but should they prove unworthy, and lose their lives because of their own defects of character, then God's holy name would be reproached. {GC 619.1}

On every hand they hear the plottings of treason and see the active working of rebellion; and there is aroused within them an intense desire, an earnest yearning of soul, that this great apostasy may be terminated and the wickedness of the wicked may come to an end. But while they plead with God to stay the work of rebellion, it is with a keen sense of self-reproach that they themselves have no more power to resist and urge back the mighty tide of evil. They feel that had they always employed all their ability in the service of Christ, going forward from strength to strength, Satan's forces would have less power to prevail against them. {GC 619.2}

They afflict their souls before God, pointing to their past repentance of their many sins, and pleading the Saviour's promise: "Let him take hold of My strength, that he may make peace with Me; and he shall make peace with Me." Isaiah 27:5. Their faith does not fail because their prayers are not immediately answered. Though suffering the keenest anxiety, terror, and distress, they do not cease their intercessions. They lay hold of the strength of God as Jacob laid hold of the Angel; and the language of their souls is: "I will not let Thee go, except Thou bless me." {GC 619.3}

Had not Jacob previously repented of his sin in obtaining the birthright by fraud, God would not have heard his prayer and mercifully preserved his life. So, in the time of trouble, if the people of God had unconfessed sins to appear before them while tortured with fear and anguish, they would be overwhelmed; despair would cut off their faith, and they could not have confidence to plead with God for deliverance. But while they have a deep sense of their unworthiness, they have no concealed wrongs to reveal. Their sins have gone beforehand to judgment and have been blotted out, and they cannot bring them to remembrance. {GC 620.1}

Because, if it could be defined as an intermittent experience, you would have achieved it the moment you became a Christian. Thus, the Christian who abides in Jesus 5% of the time has sinless perfection, in the same way that the Christian who abides in Jesus 80% of the time. But someone who has achieved sinless perfection abides in Jesus 100% of the time. It was in this condition of sinlessness that Adam lived before his transgression.

Everyone who by faith obeys God's commandments, will reach the condition of sinlessness in which Adam lived before his transgression. {Mar 224.5}

Matthew
6:22 The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light.
6:23 But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great [is] that darkness!
6:24 No man can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon.

Luke
16:13 No servant can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon.

Romans
8:9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.

As you can see, she doesn't say or imply they are still sinning. They are completely free of sin and sinning.

Try Early Writings or closing of Great Controversy.

Isn't Time of Trouble a chapter title?

Mike, what I'm saying is that the "condition of sinlessness in which Adam lived before his transgression" is that of abiding in Jesus 100% of the time. Those who don't abide in Jesus 100% of the time haven't yet reached this condition of sinlessness.

M: As you can see, she doesn't say or imply they are still sinning. They are completely free of sin and sinning.

J: But it is clear that they do not know it. . . They still fear that they may not have confessed all, even if they "cannot bring them to remembrance."