You know, I presume, about the three stages of the spiritual life? There are three stages, the purgative, the illuminative and the perfect. The saints, as a rule, lived in the way of the perfect. This level of holiness is astoundingly deep and all-encompassing, in many people almost completely devoid of venial sin. The purgative is the way of beginners, the way of detachment from the flesh, and the illuminative the way of the “proficient,” to use one of the normal terms. This person must continue detaching himself from the flesh, but also detachment of the spirit becomes a great emphasis. These stages of life are separated by great periods of suffering that purify the soul of its attachments. These steps are the normative way of spiritual growth, and the final product, the way of the perfect, is the life of saints. These are men and women so supernaturally consumed in Christ that they have ceased to live and Christ alone lives in and through them. They scarcely have venial sin left; it is an aberration, according to the sources I’ve read, rather than a common experience. Their humility is so deep that they don’t even see their radiant holiness, for their eyes are on God and they compare themselves with nothing sinful. The standard against which they compare themselves is absolutely perfect, so they always fall short, even though they scarcely do anything wrong. And, as you say, “small” imperfections are visible to them as hideous. Their sight is not impaired by sin as ours is.