How do Christians cope with the idea, that after the Day of Judgment, when all their unbelieving loved ones are cast into eternal hell, that they (the believers) will then go to heaven to worship the God who put them there?

“…to worship the God who put them there” —

Now that's simply wrong !!!

God does not send ANYONE to hell . It is a choice that each individual makes. Both angelic beings and human beings are in hell for the exact same reason: sin (ref Romans 6:23). God is completely righteous and that means a perfect combination of Mercy and Judgment.

The question is a result of a basic misunderstanding of who God is and what His being God entails.

The scripture does say God is love — “He that loveth not knoweth not God; for God is love.” [1John 4:8; KJV]. However, the scripture also declares that God is a judge — “God judgeth the righteous, and God is angry with the wicked every day.” [Psalm 7:11; KJV].

A God who is holy and a judge must hate that which is evil—that which is contrary to His goodness.

All who delight in sin deserve hell, because they have broken His law of moral perfection. If God did not send people to hell for breaking His laws, He would not be just.

But the scriptures proclaim all through that God is just 👇

The verse below is an open invitation, extended to all those who are willing to come. Jesus is eager to reveal the Father to those who are willing.

The eternal Son of God, the only mediator between God and men, the Saviour and Redeemer of lost sinners; through whose blood alone is the forgiveness of sins, says that all who acknowledges Him before men such shall not fail of being taken notice of and requited by Christ and recommended by Him to the Father to be honoured, blessed, and glorified by him.

These do not sound like a God hellbent on condemning people to hell. People do not go to hell because of Adam’s sin and consequent fall of mankind, they go to hell because of their own sin and misguided choices which they freely choose.

“But every man is tempted, when he is drawn away of his own lust, and enticed.” [James 1:14; KJV].

In fact, if God didn’t hate evil and if that hatred was not ultimately manifest in His judgment, then would it really make sense even to talk about good and evil in any objective and ultimate sense at all?