VATICAN CITY (CNS) -- Confronting and not giving in to bitterness helps priests realize that they are not all-powerful beings but sinners who have been forgiven and called by God, Pope Francis said.

Bitterness is "a subtle enemy" that hides and "robs us of the joy of the vocation we were called to," the pope said Feb. 27 in an address to clergy of the Diocese of Rome read by Cardinal Angelo De Donatis, papal vicar of the diocese.

Pope Francis was unable to attend the traditional Lenten penitential service with priests of the Diocese of Rome due to a mild cold, the Vatican said.

In his talk, titled "Bitterness in the life of a priest," the pope said his reflection was based on listening to the experiences of seminarians and priests of various Italian dioceses and did not refer "to any specific situation."

"The majority of priests that I know are happy about their lives and consider these types of bitterness as part of a normal life, without drama," he said.

The first cause of bitterness, he said, can be traced to problems with one's faith, for example, when a priest feels "deceived" by God, possibly because he "replaced hope" with his own expectations about priestly life.

More importantly, a priest's relationship with God, which helps him to "distinguish between expectations and hopes," plays an important role.

"Expectation is born when we spend our lives trying to save our lives: we get angry looking for security, rewards or promotions. When we receive what we want, we almost feel that we will never die, that it will always be so! Because we are the point of reference," the pope explained.

"Hope, instead, is something that is born in the heart when we decide not to defend ourselves anymore," he said. "When I recognize my limits and that not everything begins and ends with me, then I recognize the importance of trust."

Another source of bitterness for priests could be problems with their bishops, he said. While blaming one's superiors is a "cliche that no longer holds water," bishops too have "limitations and shortcomings" and there will always be problems with "management or pastoral styles."

Nevertheless, the pope added, priests can be embittered when they see a form of "soft authoritarianism" when priests or laity who disagree with a bishop are excluded or when "real competence is supplanted by a certain presumed loyalty."

"Certainly, in this time of widespread precariousness and fragility, the solution can seem to be authoritarianism -- in the political sphere this is evident," he said. "But the real cure -- as St. Benedict advises -- lies in equity, not uniformity."

Finally, a third source of bitterness can be seen in problems among priests themselves, especially in recent years where priests have "suffered the blows of financial and sexual scandals" in the church.

"Suspicion has made relationships drastically colder and more formal; one no longer enjoys the gifts of others," he said. "On the contrary, it seems to be a mission to destroy, minimize, make people suspicious."

Not only have recent scandals led to suspicions, they also have increased the temptation of believing a false concept of "the church militant in a sort of ecclesiological puritanism" that views what is inside the church as "impeccable and outside are those who make mistakes.”

"The bride of Christ is and remains the field in which the wheat and chaff grow together until the end of time," the pope said. "Those who have not made this evangelical vision of reality their own expose themselves to unspeakable and useless bitterness."

The mistrust sown by the "public and publicized sins of the clergy" has also made it difficult to share the faith with others and can cause priests to retreat in isolation rather than being in communion with others or share their difficulties and struggles.

Pope Francis warned priests that isolation from "grace and history" is one of the reasons that many are unable to establish meaningful relationships of trust.

One of the "favorite thoughts of the father of lies," the devil, he said, is to convince priests that their problems are "unique and insurmountable."

"The devil doesn't want you to talk, to tell, to share," Pope Francis said. "Look for a good spiritual father, a 'shrewd' old man who can accompany you. Never isolate yourself. Never!"