In 1908 Pope Saint Pius X penned an exhortation to priests, called Haerent Animo. It should be required reading of any Pope, Cardinal, Bishop, Priest.If you are a priest, go read this letter. If you are not, either email the link to your priest or print it out for him and hand it to him. May Pope Saint Pius X defend us against the snares and deceits of Modernism.
Pope St Pius X concludes with some practical measures for priests (and all, really) to grow in holiness. Emphases are mine.
COUNSELS OF PRIESTLY PERFECTION.
When the spirit of the grace of the priesthood has been restored and strengthened in the ranks of the clergy, our other proposals for reform, of whatever kind they may be, will with God’s help prove much more successful.
For this reason we have thought it well to supplement what we have already said by some points of practical advice which will give you timely aid to preserve and nourish the grace of your priesthood.
[Annual Retreat]: First, there is the pious retreat during which the soul devotes itself to spiritual exercises, as they are called. These exercises are known and approved by all, though not everyone puts them into practice; there should, if possible, be a yearly retreat, performed either alone or, preferably, in common with others, the second method being usually more productive of good results, without prejudice to episcopal regulations. We ourselves have already spoken in praise of the advantages to be derived from a retreat, on the occasion when we issued certain decrees on this subject bearing on the discipline of the clergy of Rome.
[Monthly Day of Recollection]: It will be no less profitable for souls, if a similar retreat lasting a few hours is performed each month either privately or with others. We are happy to note that in many places a custom of this kind has already been introduced, with the encouragement of the bishops who sometimes preside over the group assembled for retreat.
[Association of priests, need for Priestly Fraternity. Look at the Priestly Society of the Holy Cross]: Another suggestion which we warmly recommend is that priests, as befits brothers, should form a closer union among themselves, with the approval and under the direction of the bishop. It is strongly to be recommended that they should form an association in order to help one another in adversity, to defend the honor of their name and office against attack, and for other similar objects. But it is even more important that they should form an association with a view to the cultivation of sacred learning, particularly in order to apply themselves with greater solicitude to the object of their vocation and to promote the welfare of souls by concerting their ideas and their efforts. The annals of the Church show that at times when priests generally lived in a form of common life, this association produced many good results. Why might not one re-establish in our own day something of the kind, with due attention to differences of country and priestly duties? Might not one justifiably hope, and the Church would rejoice at it, that such an institution would yield the same good results as formerly?
There are, indeed, associations of this kind which enjoy episcopal approval; and the advantages they confer are all the greater if one becomes a member early in life, in the very first years of the priesthood. We ourselves have had practical experience of the worth of one such association and fostered it during our episcopate; even still we continue to show special consideration to it and others.
Beloved sons, it is your duty to value highly and to apply these aids to priestly grace and such other means as the watchful prudence of your bishops may suggest from time to time; thus with each passing day you will walk more <worthily of the vocation in which you are called,” honoring your ministry and accomplishing in yourselves the will of God, that is, “your sanctification”.