It is important that we recognise some difficult truths about ourselves. Jonathan Edwards, in his sermon The Spirit of Love the Opposite of a Selfish Spirit (from 1 Corinthians 13:5), gives a vivid description about what happened to mankind at the fall (Genesis 3):
The ruin that the fall brought upon the soul of man consists very much in his losing the nobler and more benevolent principles of his nature, and falling wholly under the power and government of self-love. Before, and as God created him, he was exalted, and noble, and generous; but now he is debased, and ignoble, and selfish.
Immediately upon the fall, the mind of man shrank from its primitive greateness and expandedness, to an exceeding smallness and contractedness; and as in other respects, so especially in this. Before, his soul was under the government of that noble principle of divine love, whereby it was enlarged to the comprehension of all his fellow creatures and their welfare. And not only so, but it was not confined within such narrow limits as the bounds of the creation, but went forth in the exercise of holy love to the Creator, and abroad upon the infinite ocean of good, and was, as it were, swallowed up by it, and became one with it. But so soon as he had transgressed against God, these noble principles were immediately lost, and all this excellent enlargedness of man's soul was gone; and thenceforward he himself shrank, as it were, into a little space, circumscribed and closely shut up within itself to the exclusion of all things else.
Sin, like some powerful astringent, contracted his soul to the very small dimensions of selfishness; and God was forsaken, and fellow creatures forsaken, and man retired within himself, and became totally governed by narrow and selfish principles and feelings. Self-love became absolute master of his soul, and the more noble and spiritual principles of his being took wings and flew away.