What costs nothing, but is worth everything...?

Question:

What costs nothing, but is worth everything...?

that weights nothing, but lasts a lifetime. That one person can't own, but two people can share?

Additional Details

1 week ago
Thank yu all for all the great answers!
I want to give yu a hint :) - the answer is as simple as the question...is only 1 thing... insignificant perhaps for some but very important to many...

Best Answer - Chosen by Asker: 1 week ago
Thank yu all for all the great answers!
I want to give yu a hint :) - the answer is as simple as the question...is only 1 thing... insignificant perhaps for some but very important to many...