Spritual mortification I get completly. I even get fasting, at 320 lbs I could probably use it anyway.

Beating yourself with a whip, wearing a chain, even a hair shirt seems a little extreme. With all the beauty that God has given us in the world why should we go out of our way to hurt oursleves?
Fasting, in moderation, is good for a person physically and spritually. Unless, of course, you do it in a prideful manner, “I’m so holy. I fast EVERY FRIDAY.” It is the more extreme kind that I don’t understand. It makes no sense to me to whip the body that God made or to injure it with a chain or heavy weight. I simply don’t get it. Didn’t Jesus suffer enough?
Ask and ye shall receive:
Colossians 1:24. 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:
*Wanting… There is no want in the sufferings of Christ in himself as head: but many sufferings are still wanting, or are still to come, in his body the church, and his members the faithful.
*
To overvalue the good of the body, which is food for worms and dust is foolishness from the world.

This entire world is going to be destroyed by God in fire, and all the riches in it that men cling to, all the art, all made by man’s hands from the beginning of time. Destroyed.
The ways of the world are not the ways of God. There are so many scriptural verses showing the value of suffering and the lack of value of sensual and material pleasures.
So it is that the saints desire to be as much like Christ as possible, and to make as much use of all the gifts that God gives them to gain as much merit as possible before God and to mortify the passions and do penance for their own sake and all the Church.
Those who can practice corporeal mortification definitely should. Real corporeal mortification. Try reading
the life of St. Lydwine of Schiedam.
The more you sacrifice and give up to God in this life, the more you suffer for Him and embrace the cross, the greater good you do for all the mystical Body of Christ, and the higher and closer to God and more full of His love you will be in Heaven.
For further reference:
‘Let us remember that every act of mortification is a work for heaven. This thought will make all suffering and weariness sweet.’
‘Let us read the lives of the saints; let us consider the penances which they performed, and blush to be so effeminate and so fearful of mortifying our flesh.’
St. Alphonsus Maria de Liguori
‘You must practice, at one and the same time, interior and exterior mortification; but with this difference, that you must give yourself up to the first
particularly, always, and without exception; to the second, on the contrary, only as far as circumstances and the particular condition of persons and occasions will permit.’
‘Do not wait for old age to mortify your body and your passions. First, are you sure of reaching it? Again, how shall you do penance at that age?’
St. Ignatius of Loyola
‘There were two saints in the desert, who had sewed thorns into all their clothes; and we seek for nothing but comfort!’
‘We give our youth to the devil, and the remains of our life to the Good God, who is so good that He deigns to be content with even that. . . but, happily, everyone does not do so. A great lady has been here, of one of the first families in France; she went away this morning. She is scarcely three-and-twenty, and she is rich-very rich indeed. . . She has offered herself in sacrifice to the good God for the expiation of sins, and for the conversion of sinners. She wears a girdle all armed with iron points; she mortifies herself in a thousand ways; and her parents know nothing of it. She is white as a sheet of paper. Hers is a beautiful soul, very pleasing to the good God, such as are still to be found now and then in the world, and they prevent the world from coming to an end.’
‘Oh, how bitterly shall we regret at the hour of death the time we have given to pleasures, to useless conversations, to repose, instead of having employed it in mortification, in prayer, in good works, in thinking of our poor misery, in weeping over our poor sins; then we shall see that we have done nothing for Heaven. Oh, my children, how sad it is! Three-quarters of those who are Christians labor for nothing but to satisfy this body, which will soon be buried and corrupted, while they do not give a thought to their poor soul, which must be happy or miserable for all eternity. They have neither sense nor reason: it makes one tremble.’
St. Jean Marie Baptiste Vianney, the Cure of Ars
‘I myself have undergone your penance. I only ask you for your mortification to spend one entire night without stirring on your back.’
St. Lydwine of Schiedam