When a man is under the sway of passion and prejudice he is spiritually blind. Seeing nothing but good in his own side, and nothing but evil in the other, he cannot see anything as it really is, not even his own side; and not understanding himself, he cannot understand the hearts of others, and thinks it is right that he should condemn them. Thus there grows up in his heart a dark hatred for those who refuse to see with him and who condemn him in return, he becomes separated from his fellow-men, and confines himself to a narrow torture chamber of his own making.
Sweet and peaceful are the days of the equal-minded man, fruitful in good, and rich in manifold blessings. Guided by wisdom, he avoids those pathways which lead down to hatred and sorrow and pain, and takes those which lead up to love and peace and bliss. The occurrences of life do not trouble him, nor does he grieve over those things which are regarded by mankind as grievous, but which must befall all men in the ordinary course of nature. He is neither elated by success nor cast down by failure. He sees events of his life arrayed in their proper proportions, and can find no room for selfish wishes or vain regrets, for vain anticipations and childish disappointments.
And how is this equal-mindedness - this blessed state of mind and life - acquired? Only by overcoming one's self, only by purifying one's own heart, for the purification of the heart leads to unbiased comprehension, unbiased comprehension leads to equal-mindedness, and equal-mindedness leads to peace. The impure mane is swept helplessly away on the waves of passion; the pure man guides himself into the harbour of rest. The fool says, "I have an opinion," the wise man goes about his business.
-James Allen (1864-1912), as excerpted from The Selected Teachings of James Allen Vol. II