Allan Kardec

“If we had never seen fishes, we should be at a loss to understand how any living beings could exist In the sea.”
― Allan Kardec, The Spirits' Book

“How many ills, how many infirmities, does man owe to his excesses, his ambition – in a word, to the indulgence of his various passions! He who should live soberly in all respects, who should never run into excesses of any kind, who should be always simple in his tastes, modest in his desires, would escape a large proportion of the tribulations of human life. It is the same with regard to spirit-life, the sufferings of which are always the consequence of the manner in which a spirit has lived upon the earth. In that life undoubtedly he will no longer suffer from gout or rheumatism; but his wrong-doing down here will cause him to experience other sufferings no less painful. We have seen that those sufferings are the result of the links which exist between a spirit and matter; that the more completely he is freed from the influence of matter – in other words, the more dematerialized he is – the fewer are the painful sensations experienced by him. It depends, therefore, on each of us to free ourselves from the influence of matter by our action in this present life. Man possesses free-will, and, consequently, the power of electing to do or not to do. Let him conquer his animal passions; let him rid himself of hatred, envy, jealousy, pride; let him throw off the yoke of selfishness; let him purify his soul by cultivating noble sentiments; let him do good; let him attach to the things of this world only the degree of importance which they deserve – and he will, even under his present corporeal envelope, have effected his purification, and achieved his deliverance from the influence of matter, which will cease for him on his quitting that envelope. For such a one the remembrance of physical sufferings endured by him in the life he has quitted has nothing painful, and produces no disagreeable impression, because they affected his body only, and left no trace in his soul. He is happy to be relieved from them; and the calmness of a good conscience exempts him from all moral suffering.”
― Allan Kardec, The Spirits' Book