"For behold, he did not keep the commandments of God, but he did walk after the desires of his own heart. And he had many wives and concubines. And he did cause his people to commit sin, and do that which was abominable in the sight of the Lord. Yea, and they did commit whoredoms and all manner of wickedness."
Mosiah 11:2
This is talking about King Noah, who followed Zeniff to the throne (of the Nephite offshoot that went back to live near the Lamanites). What is scary about this verse is the idea that he walked after the desires of his own heart, and how deeply that destroyed him. And I think that danger is probably there in all of us... things that we want that will destroy us, unless we work with God and allow him to change our hearts, and work at walking God's path rather than the one that we make for ourselves.
It's sometimes hard because we hear "trust your heart" (or your gut) so often, but unless our hearts are in tune with the spirit, that could be a really bad idea. However, if we are listening to the Spirit, and we are letting God have full sway in our hearts, then that could be the perfect thing. If we can't tell, then let's study and pray and practice listening to the Spirit more, so that we can be more confident in knowing when God is with us and when we are going astray. And of course, we have the scriptures and commandments to help us out, which we should absolutely follow unless the Spirit tells us otherwise. There are exceptions, like Nephi and Laban, but we shouldn't decide something is an exception unless we're certain. Let's remember how King Noah's heart betrayed him, and stay far away from that possibility.
