Like I said before, if you read in the Book of Revelation, you will see evidence that we mortals existed in heaven before coming to this earth.
Revelation 12:7-11
7 And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels,
8 And prevailed not; neither was their place found any more in heaven.
9 And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
10 And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night.
11 And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death.
In the above verses we see that Michael and his angels fought against Satan and his angels in the great war in heaven. Satan and his angels were cast out of heaven into this earth. Michael and his angels eventually sent to this earth and could overcome Satan by the blood of the Lamb and were subject unto death.
In other words, those who existed as Michael and his angels in a premortal life in heaven, were given the opportunity to come to this earth and experience mortal life where they needed the blood of the Lamb to overcome Satan and were also subject to death as mortals. Michael is Adam and we are Michael's angels are the rest of us here on earth that are given the chance to overcome Satan through the blood of Jesus Christ.
We sided with Jesus in the war in heaven where He was foreordained to be the savior of the world. Also in the premortal existence in heaven he chose some of us to be his leaders while on this earth.
John 17:24-25
24 Father, I will that they also, whom thou hast given me, be with me where I am; that they may behold my glory, which thou hast given me: for thou lovedst me before the foundation of the world.
1 Peter 1:20
20 Who verily was foreordained before the foundation of the world, but was manifest in these last times for you,
Ephesians 1:4
4 According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
The Prophet Jeremiah was foreordained to be a prophet before he was born.
Jeremiah 1:4-5
4 Then the word of the Lord came unto me, saying,
5 Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and I ordained thee a prophet unto the nations.
This is why in Ecclesiastes it tells us that our spirits will return to God upon death. A spirit cannot return to a place it has never been before.
Ecclesiastes 12:7
7 Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it.
The Apostles of Jesus understood that man's spirit pre-existed his mortal time on this earth. This is why they wondered if the blind man sinned before he was born.
John 9:1-3
1 And as Jesus passed by, he saw a man which was blind from his birth.
2 And his disciples asked him, saying, Master, who did sin, this man, or his parents, that he was born blind?
3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.
Jesus could have corrected their thinking but didn't. He simply replied that the man did not sin.
The Prophet Job tells us that when God was laying the foundations of the earth, that the sons of God were shouting for joy.
Job 38:1-7
1 Then the Lord answered Job out of the whirlwind, and said,
2 Who is this that darkeneth counsel by words without knowledge?
3 Gird up now thy loins like a man; for I will demand of thee, and answer thou me.
4 Where wast thou when I laid the foundations of the earth? declare, if thou hast understanding.
5 Who hath laid the measures thereof, if thou knowest? or who hath stretched the line upon it?
6 Whereupon are the foundations thereof fastened? or who laid the corner stone thereof;
7 When the morning stars sang together, and all the sons of God shouted for joy?
The Prophet Abraham had vision of the premortal existence and this is what he saw:
Abraham 3:22-28
22 Now the Lord had shown unto me, Abraham, the intelligences that were organized before the world was; and among all these there were many of the noble and great ones;
23 And God saw these souls that they were good, and he stood in the midst of them, and he said: These I will make my rulers; for he stood among those that were spirits, and he saw that they were good; and he said unto me: Abraham, thou art one of them; thou wast chosen before thou wast born.
24 And there stood one among them that was like unto God, and he said unto those who were with him: We will go down, for there is space there, and we will take of these materials, and we will make an earth whereon these may dwell;
25 And we will prove them herewith, to see if they will do all things whatsoever the Lord their God shall command them;
26 And they who keep their first estate shall be added upon; and they who keep not their first estate shall not have glory in the same kingdom with those who keep their first estate; and they who keep their second estate shall have glory added upon their heads for ever and ever.
27 And the Lord said: Whom shall I send? And one answered like unto the Son of Man: Here am I, send me. And another answered and said: Here am I, send me. And the Lord said: I will send the first.
28 And the second was angry, and kept not his first estate; and, at that day, many followed after him.