Mediator Dei §157

¹⁵⁷ During the days of Septuagesima and Lent, our Holy Mother the Church over and over again strives to make each of us seriously consider our misery, so that we may be urged to a practical emendation of our lives, detest our sins heartily and expiate them by prayer and penance. For constant prayer and penance done for past sins obtain for us divine help, without which every work of ours is useless and unavailing.