No matter how ugly a thing may be, there is always some beauty concealed in it; in every untruth there is a grain of truth, in everything evil a grain of goodness. This does not mean, of course, that you should abstain from criticism! You misunderstand positivity if you think that you should no longer find anything bad, ugly, etc., but positivity means that you should see the grain of beauty in everything evil. This develops the higher forces of your soul.
Source: Rudolf Steiner – GA 100 – Theosophy and Rosicrucianism: Lecture XIV: Further Stages of Rosicrucian Training – Kassel, 29th June 1907