165 Hence, the liturgical year, devotedly fostered and accompanied by the Church, is not a cold and lifeless representation of the events of the past, or a simple and bare record of a former age. It is rather Christ Himself who is ever living in His Church. Here He continues that journey of immense mercy which He lovingly began in His mortal life, going about doing good, with the design of bringing men to know His mysteries and in a way live by them. These mysteries are ever present and active not in a vague and uncertain way as some modern writers hold, but in the way that Catholic doctrine teaches us. According to the Doctors of the Church, they are shining examples of Christian perfection, as well as sources of divine grace, due to the merit and prayers of Christ; they still influence us because each mystery brings its own special grace for our salvation. Moreover, our holy Mother the Church, while proposing for our contemplation the mysteries of our Redeemer, asks in her prayers for those gifts which would give her children the greatest possible share in the spirit of these mysteries through the merits of Christ. By means of His inspiration and help and through the cooperation of our wills we can receive from Him living vitality as branches do from the tree and members from the head; thus slowly and laboriously we can transform ourselves "unto the measure of the age of the fullness of Christ."
Source: Mediator Dei (Vatican.va)