Fr Flader once told me that "the Devil hates priests - if he can get them with women, he will; if he can get them with men, he will; if he can get them with children, he will; if he can get them with alcohol, he will... the Devil hates priests." Of course, as we are not Manichæans, we know that God is infinitely above the machinations of Satan, and that God's grace and His angels are sent to all men, including priests, to guard and save them; and the grace of state that comes with Holy Orders ought suffice to keep priests on the straight and narrow path that leads to life - if, that is, life is lived with fidelity to grace, a life focussed on prayer and the Sacraments, a life of charity, hope and faith - and as part of the Divine plan, we ought intercede for each other, and especially for priests, whose calling is so supernatural, and constitutes a difficult path.
In this Year for Priests, the following indulgences have been conceded to all the faithful, precisely to encourage them to pray for priests:
The Plenary Indulgence is granted to all the faithful who are truly repentant who, in a church or in a chapel, devoutly attend the divine Sacrifice of Mass and offer prayers to Jesus Christ the Eternal High Priest, for the priests of the Church, and any other good work which they have done on that day, so that he may sanctify them and form them in accordance with His Heart, as long as they have made expiation for their sins through sacramental confession and prayed in accordance with the Supreme Pontiff's intentions: on the days in which the Year for Priests begins and ends [that is, the Feast of the Sacred Heart], on the day of the 150th anniversary of the pious passing of St John Mary Vianney [that is, the 4th of August, NOT his traditional feast day of the 8th], on the first Thursday of the month or on any other day established by the local Ordinaries for the benefit of the faithful....Lastly, the Partial Indulgence is granted to all the faithful every time they devoutly recite five Our Fathers, Hail Marys and Glorias, or another expressly approved prayer, in honour of the Sacred Heart of Jesus, to obtain that priests be preserved in purity and holiness of life.
I rather like the prayer for priests that St Thérèse composed (though I'm unsure if it is "expressly approved", yet the general grant of partial indulgence in the Enchiridion would seem to extend to it):
O Jesus, eternal Priest, keep your priests within the shelter of Your Sacred Heart, where none may touch them. Keep unstained their anointed hands, which daily touch Your Sacred Body. Keep unsullied their lips,daily purpled with your Precious Blood. Keep pure and unearthly their hearts, sealed with the sublime mark of the priesthood. Let Your holy love surround them and shield them from the world's contagion. Bless their labours with abundant fruit and may the souls to whom they minister be their joy and consolation here and in heaven their beautiful and everlasting crown. Amen.