From Dom Guéranger's The Liturgical Year.
All flesh had corrupted its way upon the earth. The terrible lesson, then, which men had received, by being driven out of paradise in the person of our first parents, had been without effect. Neither the certainty of death, when they would have to stand before the divine Judge, nor the humiliations which attend man’s first coming into this world, nor the pains and fatigues and trials which beset the whole path of life, had subdued men’s hearts, or brought them into submission to that sovereign Master whose hand lay thus heavy upon them. They had the divine promise that a Saviour should be given to them, and that this Redeemer (who was to be the Son of her that was to crush the serpent’s head), would not only bring them salvation, but would moreover reinstate them in all the happiness and honours they had lost. But even this was not enough to make them rise above the base passions of corrupt nature. The example of Adam’s nine hundred years’ penance, and the admonitions he could so feelingly give who had received such proofs of God’s love and anger, began to lose their influence upon his children; and when he at last descended into the grave, his posterity grew more and more heedless of what they owed to their Creator. The long life, which had been granted to man in this the first age of the world, was made but a fresh means of offending Him who gave it. When, finally, the sons of Seth took to themselves wives of the family of Cain, the human race reached the height of wickedness, rebelled against the Lord, and made their own passions their god.
Yet, all this while, they had had granted to them the power of resisting the evil propensities of their hearts. God had offered them His grace, whereby they were enabled to conquer pride and concupiscence. The merits of the Redeemer to come were even then present to divine justice, and the Lamb, slain, as St. John tells us, from the beginning of the world, applied the merits of His Blood to this as to every generation which existed before the great Sacrifice was really immolated. Each individual of the human family might have been just, as Noah was, and, like him, have found favour with the Most High; but the thought of their heart was bent upon evil, and not upon good, and the earth became peopled with enemies of God. Then it was that it repented God that He had made man, as the sacred Scripture forcibly expresses it. He decreed that man’s life on earth should be shortened, in order that the thought of death might be ever before us. He, moreover, resolved to destroy, by a universal deluge, the whole of this perverse generation, saving only one family. The world would thus be renewed, and man would learn from this awful chastisement to serve and love this his sovereign Lord and God.
We find the following liturgical formula in the Mozarabic missal. Nothing could be more appropriate to the season of Septuagesima.
(Dominica ante carnes tollendas.)
Ecce jam in proximo sunt dies illi salutis, in quibus revoluto anni circulo, per salutari abstinentiæ opus, remedia cupimus auscipere pravorum actuum nostrorum. Etenim sicut ait apostolus: Hoc est acceptabile tempus, et hi sunt dies salutis, in quibus spiritualis medela exquirenti adveniat animæ, et mala dulcia scrabra peccaminum evellantur a mente; ut qui consuetudine noxia semper cogimur deorsum fluere, tandem divina nos erigente dementia, conemur sursum surgere, ut horum dierum votiva exhibentes susceptione, et maiorum nostrorum levemur a crimine, et beatitudinis electorum mereamur compotes esse. Amen.
Behold, now are close at hand those days of salvation, which the cycle of the year brings round to us, and in which we desire, by the exercise of salutary abstinence, to apply a remedy to our evil doings. For, as the apostle says: This is the acceptable time, and, these are the days of salvation, wherein a spiritual cure is given to the soul that seeks it, and the evil delights of sin are rooted from the mind. Hereby, we, whose evil habits are ever forcing us to a downward tendency, are by the uplifting mercy of God, encouraged to rise above this earth; that thus, by the devout observance of what these days require, we may not only be delivered from the guilt of our sins, but may moreover deserve to be companions with the elect in eternal bliss. Amen.
 Gen vi. 12
 Apoc. xiii. 8.
 Gen. vi. 6.