When we labor for God, our labor will not be in vain  -  Isaiah 65:23

They shall not labour in vain, nor bring forth for trouble; for they are the seed of the blessed of the LORD, and their offspring with them.

When the kingdom of Jesus will be physically established, things will be totally different – the sounds of sorrow and anguish will no longer be heard, we will live to enjoy the fruit of our labor, as the realization will come that our labor is not in vain, if it was done for the Lord, and there will not be any war or calamity.