Russell says this in the "Family" chapter of Conquest of Happiness, and while he's talking about the stream of generations and the "procreative impulse" he's not saying you have to have children of your own to to feel a part of the stream of life. Or rather, he's saying that happy people claim a lasting stake in the life of their species and care about "the world that shall come after them" because we are all family, they are all our children.
That's what John Dewey meant too, when he said we're all links in the continuous human community. Personal death does not end all, the loss of those near us does not obliterate the streaming possibilities of life to come, the tragic aspect of life does not exhaust it.
But stagnation and social hostility might. We must enlarge our hearts and transcend selfish isolation. We must evolve past envy, past the age of Drumpf.
“We have reached a stage in evolution which is not the final stage. We must pass through it quickly, for if we do not, most of us will perish by the way, and the others will be lost in a forest of doubt and fear. .. To find the right road out of this despair civilised man must enlarge his heart as he has enlarged his mind. He must learn to transcend self, and in so doing to acquire the freedom of the Universe.”And with that, the secular sermon's done. Amen.
6 am/6:48, 26/35/22, 4:30