I would think that priests choose celibacy when they take Holy Orders. They don’t become priests and are then told, “By the way, you can never get married.” It’s a choice they make. As for abstaining from meat, giving up meat on wednesdays and fridays as an act of sacrifice is hardly abstaining from meat the way it is suggested in Timothy and being ungrateful for it. In fact, giving up something like meat (which was a luxury in the time lent started, we tend to take it for granted today) is showing gratitude because the point is that you’re supposed to be giving up something good that you enjoy. If meat was bad and you gave it up, it’s hardly a sacrifice, and if it’s evil and we shouldn’t be grateful for it, shouldn’t we be abstaining from it ALL the time? Or is it only evil on certain days of the year? Answer: It’s not evil at all and we should always show gratitude for everything God’s given us.
Chap. 4 Ver. 3 "Forbidding to marry, to abstain from meats. He speaks of the Gnostics, the Marcionites, the Encratites, the Manicheans, and other ancient heretics, who absolutely condemned marriage and the use of all kind of meat; because they pretended that all flesh was from an evil principle. Whereas the Church of God, so far from condemning marriage, holds it a holy sacrament and forbids it to none but such as by vow have chosen the better part: and prohibits not the use of any meats whatsoever in proper times and seasons, though she does not judge all kind of diet proper for days of fasting and penance." St. Jerome commentary on The First Epistle of St. Paul to Timothy, 4th century AD.