Men cannot, unless they are carried by Christ Himself.
Becoming a priest is a particular discernment, that requires one to give themselves up to Christ with all their will so that they may handle doing the regular liturgies, the divine office, work as a spiritual pastor to be a limb of Chirst's own shepherding, to be a rock of faith and true doctrine to be a limb of Christ's own Rock-iness… In fact, the priest himself acts in the person of Christ during the liturgy, sacramentally chosen so that his hands may be those of God when he celebrates the eucharist.
Short reply: no one can carry that on their own, but the sacraments recreate them in Christ's image.