JOEL - He can't. And one must not just be sorry for what he did; he must experience "godly sorrow".

Paul said:
"Now I rejoice, not that ye were made sorry, but that ye sorrowed to repentance: for ye were made sorry after a godly manner, that ye might receive damage by us in nothing.
For godly sorrow worketh repentance to salvation not to be repented of: but the sorrow of the world worketh death. " (2 Cor. 7:9-10)

Having the "sorrow of the world" is not enough; it only means that one regrets what he did wrong, but has no desire to change. This will not bring true forgiveness. Godly sorrow goes deep into the soul and compels one to change one's heart and make voluntary amends.

Alma describes his feelings as he began the repentance process for his sins:
"But I was racked with eternal torment, for my soul was harrowed up to the greatest degree and racked with all my sins.
Yea, I did remember all my sins and iniquities, for which I was tormented with the pains of hell; yea, I saw that I had rebelled against my God, and that I had not kept his holy commandments.
Oh, thought I, that I acould be banished and become extinct both soul and body, that I might not be brought to stand in the presence of my God, to be judged of my deeds.
And now, for three days and for three nights was I racked, even with the pains of a damned soul." (Alma 36:12-17)

Now that's Godly sorrow. Only when one experiences this(or something close to it) can they afterwards feel the incredible joy that forgiveness brings as Alma also describes when he realized that his sins were forgiven.

"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.
And oh, what joy, and what marvelous light I did behold; yea, my soul was filled with joy as exceeding as was my pain!
Yea, I say unto you, my son, that there could be nothing so exquisite and so bitter as were my pains.
Yea, and again I say unto you, my son, that on the other hand, there can be nothing so exquisite and sweet as was my joy. (Alma 36:19-21)