DI#23 The Call to the Apostolate

"PRESENCE OF GOD - I place myself in the presence of Jesus, the Head of the Mystical Body, the Church, begging Him to show me how to collaborate with Him in the work of saving souls."

"...in the actual economy of the Redemption, our collaboration is necessary" because "He has so willed it for the greater honor of His spotless Spouse."  "...the salvation of many souls depends on the prayers and voluntary mortifications offered for this end, ..."

See Pope Pius XII's encyclical here:

http://w2.vatican.va/content/pius-xii/en/encyclicals/documents/hf_p-xii_enc_29061943_mystici-corporis-christi.html