I have thought about the priesthood, but I can’t imagine not having sex at least once in my life. Wouldn’t God understand if I had it once for the sake of experiencing it?

In the same way that a man who is planning on getting married and becoming a father begins reevaluating his life in light of the responsibilities and expectations of fatherhood, so a young person thinking about the priesthood or religious life should be thinking about living up to God’s expectations—not living down to the expectations of the world.

Besides the spiritual consequences of sex, you also have to consider the fact that one act of sex could bring a child into the world. What kind of father do you want to be? A spiritual one, or a biological one? Whichever one you choose, give yourself completely to that calling. Furthermore, what about the emotional toll this will take on you and the woman? You would be using her, as you said, “for the sake of experiencing it.” This is no way to prepare to become an image of Christ in the priesthood.

As you realize, choosing the pure life is demanding. Jesus demands that all his followers be ready to make sacrifices: “No one who puts his hand to the plow and looks back is fit for the kingdom of God” (Luke 9:62). Persevere for Christ. “My son, hold fast to your duty, busy yourself with it, grow old while doing your task. Admire not how sinners live, but trust in the Lord and wait for his light” (Sir. 11:20–21, NAB).

Do not make the mistake of thinking about celibacy in negative terms. If you become a priest or religious, then the gift of your sexuality is not being wasted. Rather, you are being offered as a living sacrifice to God, for the sake of the Church. To give your virginity away to another would be like a groom losing his virginity to a stranger the night before his wedding. Make this sacrifice, as a groom waits for his bride. As Pope John Paul II said, young people “know that their life has meaning to the extent that it becomes a free gift for others.”[1]. If the Lord has called you to himself, then you are his. As Saint Francis once said to his brothers, “Hold back nothing of yourselves for yourselves so that he who gives himself totally to you may receive you totally.”[2]

As a reward for such a generous donation of self, Christ promises, “There is no one who has left house or brothers or sisters or mother or father or children or lands, for my sake and for the gospel, who will not receive a hundredfold now in this time, houses and brothers and sisters and mothers and children and lands, with persecutions, and in the age to come eternal life” (Mark 10:29–30).

Also, remember that the one-flesh union of a husband and wife is only a sign that points to an eternal reality: we all will be wedded to God in heaven. The celibacy of Catholic priests around the world is a constant witness to humanity that there is a greater reality than the daily affairs and pleasures of earth. By giving up marital intercourse in this life, you are essentially saying to God that you are skipping the sign and beginning to embrace the reality of total union with Him.

__________________________
[1]. Pope John Paul II, Crossing the Threshold of Hope (New York: Alfred A. Knopf, Inc., 1994), 121.
[2]. “A Letter to the Entire Order,” 29 in Regis J. Armstrong and Ignatius C. Brady, trans. Francis and Clare: The Complete Works (New York: Paulist Press, 1982), 58.