Alma 36:19

"And now, behold, when I thought this, I could remember my pains no more; yea, i was harrowed up by the memory of my sins no more."

Alma recounts his conversion story to his son Helaman.  Alma was a huge antagonizer of the Church and had many sins and huge guilt for all the people he led astray.  For 3 days he suffered for these sins and was miserable.  When he remembered the Savior and called upon Him, Alma was forgiven and was cleansed of his sins. The Atonement is real and really cleanses us and makes us holy.