a picture of a straight road with hills (draw or find one)
Here is another object lesson from my friend Brent Anderson, a former Seminary teacher: "This isn't so much of an object lesson, but the kids really responded to this. The straight and narrow path is, of course, straight and narrow, but that doesn't mean that the elevation stays the same. There are hills to climb (challenges to face) and valleys to descend (difficulties that we will experience)."
While traveling along a mountainous road one evening through a driving rainstorm punctuated with frequent claps of thunder and flashes of lightning, Sister Wirthlin and I could barely see the road, either in front of us or to the right and the left. I watched the white lines on that road more intently than ever before. Staying within the lines kept us from going onto the shoulder and into the deep canyon on one side and helped us avoid a head-on collision on the other. To wander over either line could have been very dangerous. Then I thought, “Would a right-thinking person deviate to the left or the right of a traffic lane if he knew the result would be fatal? If he valued his mortal life, certainly he would stay between these lines.”
That experience traveling on this mountain road is so like life. If we stay within the lines that God has marked, he will protect us, and we can arrive safely at our destination.
The Savior taught this principle when he said,
“Enter ye in at the strait gate: for wide is the gate, and broad is the way, that leadeth to destruction, and many there be which go in thereat:
“Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it.” (Matt. 7:13–14.)
In modern-day revelation he taught further, “For strait is the gate, and narrow the way that leadeth unto the exaltation and continuation of the lives, and few there be that find it.” (D&C 132:22.)
King Josiah was a king of Judah who reigned in righteousness. When he was only eight years old, he succeeded his father as king. Scripture tells us that although he was just a boy, Josiah “did that which was right in the sight of the Lord, … and turned not aside to the right hand or to the left.” (2 Kgs. 22:2.)
The Lord revealed to the Prophet Joseph Smith, “For God doth not walk in crooked paths, neither doth he turn to the right hand nor to the left, neither doth he vary from that which he hath said, therefore his paths are straight, and his course is one eternal round.” (D&C 3:2.)
Joseph B Wirthlin, The Straight and Narrow Way, General Conference, Oct 1990 https://www.lds.org/general-conference/1990/10/the-straight-and-narrow-way?lang=eng