The Israelites had certainly fell into a dark time, and it is because they began to trust in themselves, in the arm of the flesh, and not in the Lord. John 14:6, 2 Nephi 9:28-29, and Isaiah 55:8-9 further explain why it is such a good idea to follow the Lord and not man. It is because the only way to return to Him is to follow His path and His example, not what other men deem that it is good to do. It is also important to remember that He is all knowing, all powerful, so His thoughts are higher than ours, and His ways are higher than ours. We may not understand them, but we should pray to know that it is right for ourselves and then to everything in our power to follow it. Honestly, we are foolish if we think that we are more wise, even better than, God Himself.
In some things in life it is okay to follow your heart and do what you think is best - that could be the Holy Ghost guiding you. Ultimately, especially for the big decisions, it is important to make sure that you are following the path that the Lord has set out, and not what other people are telling you is the best thing to do. God knows what is best, and we would be wise to seek out what that path and then willing take whatever action is necessary to remain on that path.