39 And so, out of that ardent and zealous charity with which all Christians are bound to love the Catholic Church, they should address their prayers to heaven, but they should also offer interior acts of penance, works of virtue, sacrifices, inconveniences, and all the pains and hardships under which we labor, of necessity, in this mortal life, but which we should occasionally, take upon ourselves voluntarily, in a spirit of generosity.
Source: Meminisse Iuvat (Vatican.va)