The Lord makes it clear that those who fail to keep his commandments cannot endure his presence:
Now my son, I would that ye should repent and forsake your sins...for except ye do this ye can in nowise inherit the kingdom of God. (Alma 39:9)
...inasmuch as ye will not keep the commandments of God ye shall be cut off from his presence. (Alma 38:1)
...the Lord cannot look upon sin with the least degree of allowance. (Alma 45:16)
[Those who] obey not the gospel of our Lord Jesus Christ...shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power... (2 Thessalonians 1:8-9)
Many mistakenly think that all that is required to dwell with God is to be forgiven of one’s sins. Forgiveness of sins covers past transgression, but does not change who you are. One who is capable of sin remains capable of sin despite having been forgiven of past sin.
21 And if the Lord shall say—Because of thine iniquities thou shalt be cut off from my presence—he will cause that it shall be so.
22 And wo unto him to whom he shall say this, for it shall be unto him _that will_ do iniquity, and he cannot be saved; therefore, for this cause, that men might be saved, hath repentance been declared. (Helaman 12)
Those who will continue in sin—even if forgiven of past sin—cannot dwell with God.
But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death. (Revelation 21:8)
Jesus can temporarily admit us into his presence by forgiving us of our past sins. For example, Isaiah recoiled from God’s presence until he was told that his sins had been forgiven:
Woe is me! for I am undone; because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for mine eyes have seen the King, the Lord of hosts. (Isaiah 6:5)
However, the indescribable pain felt by those with unforgiven sin will return to such a one as soon as they sin again.
An individual capable of sin cannot dwell permanently in the presence of God, because he will soon sin again, causing him to recoil from the presence of God due to the indescribable pain of enduring his presence while in sin.