(W)e must understand that the expectation of personal perfection is a romanticism not rooted in Scripture. If I demand perfection from myself, then I will destroy myself. Many Christians vacillate between being permissive in regard to sin toward themselves on the one hand, and demanding perfection from themselves on the other. They end up battered and crushed because they do not live up to their own image of perfection.
The worst part is that often this image does not have anything to do with biblical standards, with the true law and character of God. A person builds up an image of what a Christian is like as his group or he himself projects it, and then constantly turns inward for subjective analysis and finds he does not measure up to this image. Perhaps the cruelty of utopianism is most manifest at just this point, when an individual applies his own utopianism to himself. He says, 'A Christian is like this…,' 'A Christian is like that…,' and then proceeds to an inward destruction. A Christian must understand that sin is sin, and yet know that he should not establish for himself a model of 'perfection or nothing'.
In other words, a Christian can defeat himself in two ways: one is to forget the holiness of God and the fact that sin is sin. The Bible calls us to an ever deeper commitment in giving ourselves to Christ for Him to produce His fruit through us. The other is to allow himself to be worn out by Christians who turn Christianity into a romanticism. The realism of the Bible is that God does not excuse sin, but neither is He finished with us when He finds sin in us. And for this we should be thankful.
Francis Schaeffer. No Little People. The Weakness of God's Servants (3. Kapitel).