Something you cannot do without is indispensable. Alternatively, in legal terms, it could be a sine qua non, which is an essential component of an agreement. A without which nothing.
In traditional societies, people were based in small geographic areas or
in isolated locations. They could only use the Natural Resources that were
readily available around them to try and meet their needs.
the word for something you cannot live without = a need
Need. If you can't do without something, you need it.
indispensible
Water
youre subconsciously doing something
arbitrary
Impermeable.
A single word that can be defined as (or otherwise signifies)'too important to be done without' is 'necessary.' When and where something is 'too important to be done without,' that same something is 'necessary.'
metaphor
fire
Unexpected?
The word for looking at something without turning the head is "glancing."
Well, it means someone or something does something without any warning.
The word 'drought' is a noun, a word for a long period without rain; a word for a prolonged shortage of something; a word for a thing.
Subconsciously.
Something that is done, said, or chosen without certainty.