Mosiah 4

Mormon relates that as the people of King Benjamin truly repented of their sins -

"...the Spirit of the Lord came upon them, and they were filled with joy, having received a remission of their sins, and having peace of conscience, because of the exceeding faith which they had in Jesus Christ who should come..." (Book of Mormon Mosiah 4:3)

There is much scriptural evidence of the joy felt by those who receive a remission of sins. But how do we retain this remission of sins. King Benjamin continued to explain -

"...as ye have come to the knowledge of the glory of God, or if ye have known of his goodness and have tasted of his love, and have received a remission of your sins, which causeth such exceedingly great joy in your souls, even so I would that ye should remember, and always retain in remembrance, the greatness of God, and your own nothingness, and his goodness and long-suffering towards you, unworthy creatures, and humble yourselves even in the depths of humility, calling on the name of the Lord daily, and standing steadfastly in the faith..." (Book of Mormon Mosiah 4:11)

If you do this -

"...ye shall always rejoice, and be filled with the love of God, and always retain a remission of your sins; and ye shall grow in the knowledge of the glory of him that created you, or in the knowledge of that which is just and true." (Book of Mormon Mosiah 4:12)

Simply, we must be humble, praying regularly, and standing fast in the faith or keeping the promises and covenants we have made, For -

"...this is the means whereby salvation cometh. And there is none other salvation save this which hath been spoken of; neither are there any conditions whereby man can be saved..." (Book of Mormon Mosiah 4:8)