Amen, amen I say to you, unless the grain of wheat falling into the ground die, itself remaineth alone. But if it die, it bringeth forth much fruit. He that loveth his life shall lose it; and he that hateth his life in this world, keepeth it unto life eternal. (John 12:24,25)
Die by the unbelief of the Jews, be multiplied by the faith of the nations
The Lord Jesus was himself that grain which should die and be multiplied; die by the unbelief of the Jews, be multiplied by the faith of the nations. But now, encouraging us to follow in the footsteps of his Passion, he says: “He who loves his life, shall lose it.” This may be understood in two ways. First, he who loves his life, shall lose it; you love, you shall lose. If you desire to possess life in Christ, do not fear death for the sake of Christ. Second, in another way: he who loves his life, shall lose it; love not, lest you lose; love it not in this life, lest you lose it in life everlasting.
Detachment from the world (“Not of this world”)
But what I have said last, seems better to correspond with the meaning of the Gospel; for there follows: “And he who hates his life in this world, keeps it unto life eternal.” Therefore, in what was said above: “He who loves (that is, in this world [= attachment]), he of course shall lose it. But he who hates (that is, in this world [= detachment]) is he who shall keep it unto life eternal.” A great and wonderful saying, that in proportion as a man loves his life, it perishes; and as he hates, so it lasts. If you have loved it ill, then you have hated it; if you have hated it well, then you have loved it. Happy are they who, hating their life, keep it, lest they should lose it by loving.
Suffer like Christ; and beware of trying to take a shortcut into blessed eternity
But take care lest there steal upon you a desire for self I destruction, understanding this in the sense that it is your duty to hate your life in this world. For on such grounds certain wrong-minded and perverted men, who with regard to themselves, are murderers of a specially cruel and impious character, give themselves to the flames, suffocate themselves in the waters, dash themselves into pieces by casting themselves headlong, and perish. Christ did not teach this; for he, when the devil suggested to him that he should cast himself headlong, answered: “Return from where you came, Satan, for it is written: ‘You shall not tempt the Lord your God.'” And he said to Peter, signifying by what death he should glorify God: “When you were young, you did gird yourself and walked where you would, but when you are old, another shall gird you, and lead you where you are not able to go.” In this passage he made it sufficiently plain that he who follows in the footsteps of Christ must not be slain by himself, but by another.
– St Augustine, Bishop, Treatise 51 on John, from: An Approved English Translation of the Breviarium Romanum, Burns & Oates, London, 1964 (headings in bold added afterwards)