People will mourn when they see Jesus in the clouds gathering the saints to heaven (the great multitude) because the world will be left behind.
The test of faith is in our daily lives right now.
If you read 1 Thessalonians 4:13-17 attentively you will notice that there is no mention that Jesus will return to Heaven with someone...--->Jesus will not make a U-Turn to return to Heaven.
The text is talking about Jesus who will descend from Heaven with those who SLEEP IN JESUS
verse 14 [DEAD BELIEVERS WHOSE SOULS ARE IN HEAVEN] to be resurrected here on the Earth.
-->Then the believers still alive and REMAIN will be caught up together with the resurrected believers to meet Jesus in the CLOUDS IN THE AIR to WHERE Jesus will be AT HIS COMING ..IE over the valley of Meggido ...
1 Thessalonians 4:13-17
13 But we would not have you ignorant, brethren, concerning them that fall asleep; that ye sorrow not, even as the rest, who have no hope.
14
For if we believe that Jesus died and rose again, even so them also that are fallen asleep in Jesus will God BRING with him.
15 For this we say unto you by the word of the Lord,
that we that are alive, and REMAIN UNTO THE COMING of the Lord, shall in no wise precede them that are fallen asleep.
16
For the Lord himself shall DESCEND from heaven, with a shout, with the voice of the archangel, and with the trump of God: and
THE DEAD in Christ shall rise first; 17 then we that are ALIVE, and REMAIN, shall together with them be caught up in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
The test of faith is in our daily lives right now.
The test of faith during the last 42 months who will precede the Coming of Jesus will be far more harder than that for all the Christians who will have the misfortune to be alive on the Earth ...
The test of faith will goes like this Revelation 14:9-15....
[ don't expect that you will be raptured to Heaven to avoid -that test of faith- if you have the misfortune to be alive during those times ]...
Revelation 14:9-15
9 And another angel, a third, followed them, saying with a great voice,
If any man worshippeth the beast and his image, and receiveth a mark on his forehead, or upon his hand, 10 he also shall drink of the wine of the wrath of God, which is prepared unmixed in the cup of his anger; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb: 11 and the smoke of their torment goeth up for ever and ever; and they have no rest day and night, they that worship the beast and his image, and whoso receiveth the mark of his name.
12
Here is the patience of the saints, they that keep the commandments of God, and the faith of Jesus.
13
And I heard the voice from heaven saying, Write, Blessed are the dead who die in the Lord from henceforth: yea, saith the Spirit, that they may rest from their labors; for their works follow with them.
14 And I saw, and behold, a white cloud; and on the cloud [I saw] one sitting like unto a son of man, having on his head a golden crown, and in his hand sharp sickle.
15 And another angel came out from the temple, crying with a great voice to him that sat on the cloud, Send forth thy sickle, and reap: for the hour to reap is come; for the harvest of the earth is ripe.
Jesus in verse 15 is preparing to harvest the SOULS of the Christians who will be beheaded during the 42 months Reign of the Beast ie--->Those who will refuse the mark of the beast...and who will refuse to worship the Beast and his image
They are seen arriving in Heaven in Revelation 15:2 Standing on the Sea of Glass.
2 And I saw as it were a sea of glass mingled with fire;
and them that come off victorious from the beast, and from his image, and from the number of his name, standing by the sea of glass, having harps of God.
3 And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, O Lord God, the Almighty; righteous and true are thy ways, thou King of the ages.