I think that discernment of a potential call to the priesthood is, for the man considering the possibility, a very personal thing. Any man who enters seminary with a serious sincerity has a very real sense that he is being drawn to something special and strongly desires to serve.
Then reality sets in. This can shake a guy. He learns that not everything is a wonderful walk through the garden with Jesus. You’re dealing with fallen people in a fallen world.
To boot, seminary is an environment like no other; which carries its own challenges. You have to come to terms with bureaucracies, politics, ideologies, personalities, practices which you may be uncomfortable with; all under a certain trial of stress and with great intensity.
Add to that the expectations of others in a family or at the parish who are, perhaps, unwittingly making more out of your situation than they should in their excitement and naivete. Or, conversely, a man may be having to deal with lots of dumb questions about, “Why in the world would you want to do THIS?” and battles with loved ones who don’t want him to go down this path.
So one day, he’s on a high, being pumped up and looked up to by everyone around him. The next day, he’s in the doldrums of “real life.”
On a side note, one former seminarian I know has satired this scenario well by noting how a lot of priests discover certain attractive vices, precisely due to such stresses. “It no wonder,” he says, “…that in 2nd year formation/study he turns to smoking!” (3rd year to food, 4th year to alcohol) creating a stereotypical stressed out priest who’s fat, smoking, run down, desperate for some sense of control in life, and drinks too much. (A scenario which, unfortunately, carries too much truth sometimes.)
Basically, once you get inside this system, you are dealing with things in a different way than before… its like seeing what really goes on within the sausage factory. That can not but affect a man - for life. His entire perspective on the Church is changed from that which the average layman experiences and how he understands the Church. The seminarian even gets to know priests in a different way, in a more personal manner. He comes to appreciate something of how a priest’s personal trials and struggles, even the difficult way that he experiences his parish community or others to whom he has to minister.
The seminarian may want spiritual growth which isn’t being fostered. He might face hardship in studies. His superiors may make life difficult. Or he might be at odds with his desires against those of others.
So, plainly, it is hard and challenging to be a seminarian, in practice. Really, I think that it can in some ways only be compared to the stresses which a man at war must endure. But, perhaps even more intense, since the seminarian is forced to go deeper, inside himself, to discover certain things about his personality, his beliefs, his relationships with others, his God. “What does it all mean? How am I to proceed? What can I do?” And he might not like where things are headed. He tries to find answers, but they may not readily come with clarity… or he just doesn’t like what he’s hearing and has to face.
At some point, if he has to leave (either through his own decision or someone else’s), it can leave him shaken, frustrated, disappointed, disillusioned. He may not receive a lot of support from the seminary, his superiors, his friends, his parish. He can find himself significantly isolated and have a hard time readjusting to “regular life.” And, now, he is in a unique spot in this world, being someone who sees the world, life in it, and people in general by a wounded (yet somewhat enlightened) way. He is also someone who has experienced something that not many are able to understand. His interactions with others around him might, therefore, be tense. It is quite likely that he, literally, wanders alone (at least initially, though perhaps for an extended time, too) and has to find his new way. That’s tough.