2nd Nephi Chapter 10

23 Therefore, cheer up your hearts, and remember that ye are free to act for yourselves—to choose the way of everlasting death or the way of eternal life.
24 Wherefore, my beloved brethren, reconcile yourselves to the will of God, and not to the will of the devil and the flesh; and remember, after ye are reconciled unto God, that it is only in and through the grace of God that ye are saved.
25 Wherefore, may God raise you from death by the power of the resurrection, and also from everlasting death by the power of the atonement, that ye may be received into the eternal kingdom of God, that ye may praise him through grace divine. Amen.

See? Cheer up! It's so easy! Or is it?

2 Nephi 2:16 teaches us that we couldn't act for ourselves save it should be that we are enticed by the one or the other. Satan is real. He is as real as Christ. His enticings are as real as the promises of Christ. We must accept this truth and be prepared to be tempted as much as we rely on the promptings of the Holy Ghost. "If we are prepared...we shall not fear."

As we learn to recognize the temptings of Satan, we will be able to see the distinction between thoughts put into our minds through Satan and his followers, our own thoughts, and those impressions by the Holy Ghost. As we familiarize ourselves with these 3 distinct entities...we gain power in our life and in the ability to recognize the promptings we should heed and those that we must shun.

And this....is what Jacob is teaching us will give us true happiness that will cheer our hearts in this life and in the life hereafter.