85 And if belonging to it, living according to its spirit, laboring for its increase and placing its benefits at the disposition of that portion of mankind also which as yet has no part in them, means in our days having to face obstacles and oppositions as vast and deep and minutely organized as never before, that does not dispense a man from the frank, bold profession of our Faith. Rather, it spurs one to stand fast in the conflict even at the price of the greatest sacrifices. Whoever lives by the spirit of Christ refuses to let himself be beaten down by the difficulties which oppose him, but on the contrary feels himself impelled to work with all his strength and with the fullest confidence in God. He does not draw back before the straits and the necessities of the moment but faces their severity ready to give aid with that love which flees no sacrifice, is stronger than death, and will not be quenched by the rushing waters of tribulation.
Source: Summi Pontificatus (Vatican.va)