“In diagnosing physical disease, we are assisted by symptomology. Pain is man’s kindest benefactor, often revealing to him his plight in time to apply a remedy. When, however, the reason becomes ill because of some abnormal attitude, the afflicted one is the last to see the symptoms, and too often it is another who feels the pain of the infection. When turned awry, the mind loses its own sense of proportion, becoming incapable of recognizing its own infirmities. Bound as to a wheel by faulty reckoning, it goes round and round upon the axis of its notion, oblivious to the errors of its perspective. A person thus distressed can see the faults of every other man, but of his own is blissfully ignorant, yet willfully so. When his unreasonable purposes begin to bear fruit in the form of various ills, someone else is to blame – never himself.” Manly P. Hall, from “Right Thinking”
Abnormal thinking is usually devoid of the perspective which naturally aligns right thinking with wisdom. Right thinking requires honesty with oneself, a willingness to be vulnerable to both God and men, and and a regular and deep purging of unreasonable (typically self-centered) purposes.