A comfortable old age is the reward of a well-spent youth. Instead of its bringing sad and melancholy prospects of decay, it would give us hopes of eternal youth in a better world.
In the world at large, people are rewarded or punished in ways that are often utterly random. In the garden, cause and effect, labor and reward, are re-coupled. Gardening makes sense in a senseless world. By extension, then, the more gardens in the world, the more justice, the more sense is created.
To work without attachment is to work without the expectation of reward or fear of any punishment in this world or the next. Work so done is a means to the end, and God is the end.
And, behold, I come quickly; and my reward is with Me, to give every man according as his work shall be. I am Alpha and Omega, the beginning and the end, the first and the last.