Negation: ne, the neni- words and nek

Move ne and you change the claim, with the same four words each time. Mi ne diris tion denies the saying: a plain denial. Ne mi diris tion denies the subject: somebody said it, just not me. Mi diris ne tion denies the object: I said something, only not that. English handles this with stress, which works aloud and dies on the page. Esperanto parks the emphasis in the word order, where nobody can mishear it.

Mal- builds the polar opposite; ne merely rules something out, and between them sits a whole neutral middle of fine, coping and unreadable. Which is why mi ne estas malfeliĉa is a perfectly ordinary sentence: it denies misery without promising joy. No rule is broken by having both in one clause, because the one-negative-per-clause budget counts clause negatives and mal- is word-building. Bolt ne onto everything and you sound evasive; bolt on mal- and you sound melodramatic.