16 But such zeal for God's service as that demands a soul so prepared for hardships that it will not avoid labor or trouble of any kind, and that is the second quality that was conspicuous in St. Paul. For when the Lord had said to him: "I will show him how great things he must suffer for my name's sake," [ Acts ix:16] he so eagerly embraced suffering that he could write: "I exceedingly abound with joy in all our tribulations." [II Cor . vii:4] Indeed if this patient endurance of hardships is conspicuous in a preacher, it effaces whatever human weakness there is in him and wins from God the grace to produce fruit and gains for his apostolate, to a degree beyond belief, the favor of Christian people. On the other hand but little success in moving hearts is attained by those who, wherever they go, immoderately desire the comforts of life, and provided they deliver their sermons, put their hand to scarcely any other work of the sacred ministry, and the result is that they appear to be seeking their own ease rather than the good of souls.
Source: Humani Generis Redemptionem (Vatican.va)