Q. How do I know that I have a vocation?
A. A vocation to the priesthood is simply God's will that you become a priest. The problem arises in knowing God's will for you in this life. Vocations do not usually happen by visions or interior voices, but rather by signs — signs in your character, piety, and inclinations that the Holy Ghost is moving you to the priesthood. These are the ordinary signs of vocation:
A genuine and constant inclination of mind to serve God as a priest. You feel attracted to the life the priest, and to ecclesiastical things. You might be interested in the liturgy, sacred dogma, or missionary work. There is something about the priesthood that draws you.
A genuine desire to promote the glory of God and of His Church, and the salvation of souls. This is the real work of the priest, and at times demands great sacrifices. This is the only true motive of becoming a priest. It would be wrong to become a priest for the wrong motive, for example, because people would have great respect for you.
A good moral life. One of the signs of not having a vocation is the inability to stay out of mortal sin for a long time. But this requirement does not mean you must be a saint to consider the priesthood; it simply means that you must be serious about your spiritual life, that you frequent the sacraments often, avoid occasions of sin, and lead an upright life.
Piety. The life of a priest is a life of prayer, and part of a vocation to the priesthood is an inclination to prayer - liturgical prayer and private prayer.
Emotional stability. The priest must be a father to all, and must bear the problems of all, and cannot himself be burdened with emotional and psychological problems.
At least average intelligence. The priest must faithfully transmit Catholic doctrine to the faithful, and accurately diagnose their sins in the confessional. Hence he must have at least average intellectual ability to pass his seminary courses.
Good physical health. The priest must be in good physical condition in order to carry out his work. Those who suffer from chronic illnesses or who are handicapped cannot enter the priesthood.