What is Mortification?

According to Fr. John Hardon's Modern Catholic Dictionary:

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MORTIFICATION. The practice of Christian asceticism in order to overcome sin and master one's sinful tendencies, and through penance and austerity to strengthen the will in the practice of virtue and grow in the likeness of Christ. Natural mortification is a normal part of self-discipline; supernatural mortification, based on faith, seeks to grow in holiness through merit gained by co-operating with the grace of God. (Etym. Latin mortificatio, a killing, a putting to death.)
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According to Sacred Scripture...

"For if you live according to the flesh, you shall die: but if by the Spirit you mortify the deeds of the flesh, you shall live." (Rom 8:13)

"Jesus said to his disciples: If any man will come after me, let him deny himself, and take up hi scross, and follow me. For he that will save his life, shall lose it: and he that shall lose his life for my sake, shall find it. For what doth it profit a man, if he gain the whole world, and suffer the loss of his own soul? Or what exchange shall a man give for his soul?" (Matt 16:24-26)

"And he said to all: If any man will come after me, let him deny himself, and take up his cross daily, and follow me." (Lk 9:23)

"I beseech you therefore, brethren, by the mercy of God, that you present your bodies a living sacrifice, holy, pleasing unto God, your reasonable service." (Rom 12:1)

"If then you be dead with Christ from the elements of the world, why do you yet decree as though living in the world?" (Col 2:20)

"Mortify therefore your members which are upon the earth; fornication, uncleanness, lust, evil concupiscence, and covetousness, which is the service of idols." (Col 3:5)

"I chastise my body, and bring it into subjection: lest perhaps, when I have preached to others, I myself should become a castaway." (1 Cor 9:27)

"I die daily, I protest by your glory, brethren, which I have in Christ Jesus our Lord." (1 Cor 15:31)

"Always bearing about in our body the mortification of Jesus, that the life also of Jesus may be made manifest in our bodies." (2 Cor 4:10)

"With Christ I am nailed to the cross. And I live, now not I; but Christ liveth n me." (Gal 2:19, 20)

"And they that are Christs's have crucified their flesh, with the vices and concupiscences." (Gal 5:24)

"Who now rejoice in my sufferings for you, and fill up those things that are wanting of the sufferings of Christ, in my flesh, for his body, which is the church." (Col 1:24)

"Having therefore these promises, dearly beloved, let us cleanse ourselves from all defilement of the flesh and of the spirit, perfecting sanctification in the fear of God." (2 Cor 7:1)

Mortification with Prudence

According to Venerable John Paul II:

"It is not suffering for its own sake that a Christian seeks, but love. When the cross is embraced it becomes a sign of love and of total self-giving. To carry it behind Christ means to be united with him in offering the greatest proof of love." (John Paul II, Message to Youth, on XVI World Youth Day).

"From childhood, everyone is called to mortification and fasting in order to grow in character and self-discipline, overcoming the desire to possess everything for oneself alone. What we learn in the family stays with us throughout life." (John Paul II, Message for Lent, 1994)

According to Cardinal Georges Cottier, theologian of the papal household under Ven. John Paul II:

"Spiritual masters insist this practice [of mortification] must always be prudent and never without a spiritual guide [because] pathological abuses are always possible." [Cardinal Georges Cottier, Feb 4, 2010, written response to questions from Catholic News Service]

According to Pope Benedict XVI:

"Prosper of Aquitaine...left us a rich and varied teaching on Christian asceticism. He reminds us that a courageous commitment towards perfection requires constant vigilance, frequent mortifications, even if with moderation and prudence, and assiduous intellectual and manual labour to avoid idleness (cf. Epp. 125, 11; 130, 15), and above all obedience to God: "Nothing... pleases God as much as obedience..., which is the most excellent and sole virtue" (Hom. de Oboedientia: CCL 78, 552)." [Pope Benedict XVI, General Audience, 14 Nov 2007]

"Jesus' invitation to take up one's cross and follow him may at first sight seem harsh and contrary to what we hope for, mortifying our desire for personal fulfilment. At a closer look, however, we discover that it is not like this: the witness of the saints shows that in the Cross of Christ, in the love that is given, in renouncing the possession of oneself, one finds that deep serenity which is the source of generous dedication to our brethren, especially to the poor and the needy, and this also gives us joy." [Pope Benedict XVI, General Audience, 6 Feb 2008]