(2Th 1:9-10 ESV) 9 They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might, 10 when he comes on that day to be glorified in his saints, and to be marveled at among all who have believed, because our testimony to you was believed.
We were born and have lived our days in God’s presence, even if we haven’t always been believers. God is present within his Creation, and surely his presence is part of the joy of life.
And so we have no idea of what it would be like to live apart from God — truly separate. It’s not possible in this world, although we can certainly turn our backs on him. We can. But we can’t entirely escape God’s presence. God will still bring rain on the just and the unjust.
Hell may well be utter separation from God. We have no concept of how horrible that would be — but Paul warns us that it’s a dreadful punishment to suffer. Indeed, I’m certain that many of those who suffer such a horrible fate will beg for destruction.