Therefore put to death your members which are on the earth: fornication, uncleanness, passion, evil desire, and covetousness, which is idolatry. (Colossians 3:5)
And those who are Christ’s have crucified the flesh with its passions and desires. (Galatians 5:24)
For if you live according to the flesh you will die; but if by the Spirit you put to death the deeds of the body, you will live. (Romans 8:13)
And if your eye causes you to sin, pluck it out. It is better for you to enter the kingdom of God with one eye than to have two eyes and be thrown into hell. (Mark 9:47)
Even taking into consideration Christ’s hyperbole, it’s quite clear that corporal mortifications are encouraged by our Lord, the Apostles and the Saints. It also seems clear that those who look down on mortification in principle—not just in practice—are contradicting two thousand years of Catholic spirituality.
That being said, of course extreme mortifications should not be done without the consent of one’s spiritual director.
Mortification, Catholic Encyclopedia