All of these resources are finite
All of these resources are finite. Knowledge, energy and purchasing power are replenishable. Time is the only resource that is finite that cannot be replenished, and therefore the most valuable.
— from Fuel (Energy)
In the book
And here is the sober truth that sets up everything ahead. Knowledge, energy, and purchasing power are all real resources, and they are all replenishable — you can make more of each. You can rest and refuel. — Fuel (Energy)
I said it in the last chapter and it bears repeating, because it is the hinge of a life: knowledge, energy, and purchasing power are all replenishable — you can always make more of each. Time alone is finite; it is the one resource you can only ever spend. And because it can never be bought back, its scarcity is the very thing that makes it precious — it is valuable precisely because there is never enough of it. — Time