Actually, the discipline is part of religious life. John Paul II was not a religious. He was a secular. He studied in a secular seminary for a specific diocese. Seculars are not bound to all the rules that govern the consecrated life. However, there have been many secular deacons, priests, bishops and popes who have adopted many practices from religious lfie. St. John Vianney is one of them, because they were useful for them.
But these kinds of disciplines are not required of secular seminarians. Secular seminarians have always followed the same rules of discipline as the laity. Whatever discipline was in place for the laity, that what a secular seminarian, deacon, priest, bishop or pope is bound to follow, even to this day. Remember, even though they are clerics, they don’t want to give up being part of the secular world. The Church does not want them to do so either. It’s the old paradigm of being in the world, but not of the world.
The religious are an entirely different package. But that’s not for this thread. Suffice it to say that John Paul borrowed this from the religious orders because it met a spiritual need. This was most probably guided by either a member of a religious order or a secular priest who was well versed in the spirituality of religious life. You can’t engage in this kind of discipline without guidance. If you do, you run the risk of not achieving discipline. You’ll either be too laxed or too harsh.
Fraternally,
Br. JR, OSF