Is there a limit on repenting? If I have to ask forgiveness for the same thing over and over, will I reach a limit at some point?

There are two things to remember here: (1) God’s mercy is indeed infinite, and (2) true repentance means forsaking your sins.

On the one hand, because of the infinite Atonement of Jesus Christ, repentance is available to everyone, even those who have made the same mistakes many times. As the prophet Alma said, “Behold, [the Lord God] sendeth an invitation unto all men, for the arms of mercy are extended towards them, and he saith: Repent, and I will receive you” (Alma 5:33).

On the other hand, the Prophet Joseph Smith taught, “Repentance is a thing that cannot be trifled with every day. Daily transgression and daily repentance is not that which is pleasing in the sight of God” (Teachings of Presidents of the Church: Joseph Smith [2007], 73).

So what is the key to repentance? As the Lord revealed to Joseph Smith, “By this ye may know if a man repenteth of his sins—behold, he will confess them and forsake them” (D&C 58:43). And as Alma taught, “Whosoever repenteth shall find mercy; and he that findeth mercy and endureth to the end the same shall be saved” (Alma 32:13; emphasis added).

In other words, you must confess and forsake your sins and try to be faithful until the end of your life. If you are having trouble overcoming a particular sin, don’t give up on yourself in the mistaken belief that there’s a limit to sincere repentance. Seek help from your parents and your bishop or branch president. Their love, support, and counsel can help you as you strive to remove sin from your life and draw closer to Heavenly Father and Jesus Christ.