Mormons believe what Nephi wrote:
"For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do." - 2 Nephi 25:23
https://www.lds.org/study/scriptures/bofm/2-ne/25?lang=eng