If I want to know the central promise of the Gospel, I need listen no further than Revelation 21:4-8.

4“And God shall wipe away all tears from their eyes! And there shall be no more death or sorrow or crying. Nor shall there be any more pain. For the first things are passed!”
5"And He who sat upon the throne, said, 'Behold, I make all things new!' And He said to me, 'Write. For these things are faithful and true.'
6"And He said to me, 'It is done. I am Alpha and Omega, the beginning and the end. I will give freely from the well of the water of life to him who is thirsty.
7'He who overcomes, shall inherit all things. And I will be his God. And he shall be My Son.
8'But the fearful and unbelieving, and the abominable and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall take their place in the lake which burns with fire and brimstone; which is the second death.'”

Sin and pain have no remedy in this life, only in the next. But thankfully, that remedy is not based on anything I do (vv4-7). However, if what I do is based on "my truth" rather than the Truth of God, the remedy is void (v8).

My only hope is the same as my only stumbling block: Jesus Christ.

Earthly lives matter.
Eternal lives matter more.