“Every Christian has two births, the old and fleshly, and the spiritual and new, and each is opposed to the other. The fleshly birth is flesh and the spiritual birth is spirit. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit (Jn. 3:6). Because each of these births is opposed to the other then from this arises a conflict and struggle between a Christian’s flesh and spirit.
The flesh lusts against the spirit and the spirit against the flesh (Gal. 5:17).
The flesh desires to kill the spirit, and the spirit the flesh. The flesh desires to bring the spirit into submission, and the spirit the flesh. The flesh desires to rule the spirit, and the spirit the flesh.
The flesh desires to be proud, to be magnified and to be conceited, but the spirit does not wish this, but it desires to be humble-minded.
The flesh desires to fornicate and to commit adultery, but the spirit is repelled by it and desires to be chaste.
The flesh desires to seize that which is another’s, to steal and to plunder in every manner, but the spirit is repelled by this and desires to give of its own.
The flesh desires to be malicious, to flatter, to life, to be crafty, to deceive, and to be hypocritical, but the spirit hates this and desires to be truthful and to be straightforward in all dealings.
The flesh desires to hate a man, but the spirit desires to love him.
The flesh desires to wander, to be drunk, and to arrange banquets and feasts, but the spirit turns away from this and desires to live either moderately or to fast.
The flesh desires to seek glory, honor and riches in this world, but the spirit scorns all this, and strives only for eternal blessings, and so on.
Thus the flesh lusts against the spirit and the spirit against the flesh. As one renewed, a Christian should not live according to the flesh, but according to the spirit, and should subjugate the flesh to the spirit, according to the Apostolic injunction, Walk in the Spirit and you shall not fulfill the lust of the flesh (Gal. 5:16). And this is to crucify the flesh with the affections and lusts (Gal. 5:24). Make not provision for the flesh, to fulfill the lusts thereof (Rom. 13:14). Abstain from fleshly lusts, which war against the soul (1 Peter 2:11). Walk in the newness of life (Rom. 6:4). Let us not allow sin to reign in us, but let us live for Christ Who died for us, and arose again (2 Cor. 5:15).
Beloved Christians, let us see whether we have this warfare, whether we take part in this saving struggle, whether we walk in the newness of life, whether we oppose the inclinations and desires of the flesh, and whether we do not allow sin to reign over us and to rule us. For only those who have crucified the flesh with its passions and desires are Christians. What use is it to be called Christians, yet not truly be Christians? It is not the name of Christian that shows the true Christian, but the struggle against the flesh and against every sin. We must not permit the flesh everything it demands. It demands food, it demands drink, it demands clothing, it demands rest , and more: let us give what is needful, but when it desires what is contrary to the will of God and to His Law let us not permit it, that we may be Christians not only in name but also in fact.” (St. Tikhon of Zadonsk, Journey to Heaven, pp 51-53)