“must”

To do as a requirement; indicates that the sentence subject is required as an imperative or directive to execute the sentence predicate, with failure to do so resulting in a failure or negative consequence.

Every individual or anything of the given class, with no exceptions (the noun or noun phrase denoting the class must be plural or uncountable).

Used to express the future tense, sometimes with an implication of volition or determination when used in the first person. Compare shall.

Do not (negative auxiliary).

A requirement for something; something needed.

One cannot obtain what one desires by being cautious; one must be aggressive.

The world, a place where darkness and death are figurative valleys one must walk through as part of the human experience.