The church is vague about what types of ‘sins’ will keep you out of heaven. They utilize this ambiguity in a way to keep your mind thinking constantly about ALL your actions.
“…I cannot tell you all the things whereby ye may commit sin; for there are divers ways and means, even so many that I cannot number them. But this much I can tell you, that if ye do not watch yourselves, and your thoughts, and your words, and your deeds, and observe the commandments of God, and continue in the faith of what ye have heard concerning the coming of our Lord, even unto the end of your lives, ye must perish.”
~Book of Mormon, Mosiah 4:29-30~
This type of instruction is so unclear, that even the most devout members can never be certain if they’re doing good enough at any given time.