Apostasy is always characterized by a person become his or her own law. Brigham Young said this:
You have known men who, while in the Church, were active, quick and full of intelligence; but after they have left the Church, they have become contracted in their understandings, they have become darkened in their minds and everything has become a mystery to them (see Alma 12: 11), and in regard to the things of God, they have become like the rest of the world, who think, hope and pray that such and such things may be so, but they do not know the least about it. This is precisely the position of those who leave this Church; they go into the dark, they are not able to judge, conceive or comprehend things as they are. They are like the drunken man—he thinks that everybody is the worse for liquor but himself, and he is the only sober man in the neighborhood. The apostates think that everybody is wrong but themselves (“Chapter 12: Preventing Personal Apostasy,” Teachings of Presidents of the Church: Brigham Young, (1997).
In this same regard, Brigham Young taught:
Many imbibe [conceive] the idea that they are capable of leading out in teaching principles that never have been taught. They are not aware that the moment they give way to this hallucination the Devil has power over them to lead them onto unholy ground…. (same source as above).
Elder Quentin Cook of the Quorum of the Twelve Apostles said, “Some in their spiritual immaturity attempt to appear sophisticated and intellectual. Instead of accepting revelation, they want to dissect it and add dimensions and variations of meaning that distort its beautiful truths.” He continued:
“Today there is a tendency among some of us to “look beyond the mark” rather than to maintain a testimony of gospel basics. We do this when we substitute the philosophies of men for gospel truths, engage in gospel extremism, seek heroic gestures at the expense of daily consecration, or elevate rules over doctrine. Avoiding these behaviors will help us avoid the theological blindness and stumbling that Jacob described.”
“Another sign of spiritual immaturity and sometimes apostasy is when one focuses on certain gospel principles or pursues “gospel hobbies” with excess zeal. Almost any virtue taken to excess can become a vice.”
“The Lord said regarding important doctrine, “Whosoever declareth more or less than this, the same is not of me” (D&C 10:68) and “That which is more or less than this cometh of evil” (D&C 124:120). We are looking beyond the mark when we elevate any one principle, no matter how worthwhile it may be, to a prominence that lessens our commitment to other equally important principles or when we take a position that is contrary to the teachings of the Brethren.” (“Looking beyond the Mark,” Elder Quentin L. Cook, Ensign, March 2003.)
Elder Neal A. Maxwell taught,
“Great care must be exercised, however, so that in all of this, we do not pass off our personal preferences as the Lord’s program; we must not confuse our personal religious hobbies with His orthodoxy. Nor must we ever pass off a personal obsession as a spiritual impression” (Neal A. Maxwell, “True Believers In Christ,” BYU Devotional, 1980).
Alma is correct: if we have “hardened our hearts against the word, insomuch that it has not been found in us, then will our state be awful, for then we shall be condemned” (Alma 12:13).