It doesn't make sense here saying "You don't have enough courage to make a mistake!" I would have think it means "Try to make a mistake and see what will happen!" as there is a entry in dictionary which is "[with obj. and infinitive] defy or challenge (someone) to do something", but the part of speech is a regular verb whereas in the sentence I provided it's a modal verb.
I don't think dare is a "modal" verb in OP's cited context. It's what's called a...
The word catenative comes from the Latin catena meaning "chain". Catenative verbs combine with other verbs and can form a chain of two or three or more verbs. (englishclub.com)
A main verb (ie lexical verb, not auxiliary or modal) that can be followed by another main verb is known as a catenative verb. In the following examples, the verbs want and like are catenative:
I want to eat.
I like eating.
As this chart shows, dare is one of a small number of verbs that can (optionally) be followed by a "bare infinitive" (without the infinitive marker to)...
Other catenative verbs that don't need to include hear, help, let, make, as described here. Note that Don't you dare [to] be late! is like He helped [to] wash the dishes or He makes me [to] lie down in green pastures, in that the word to is effectively "optional" in such constructions. But with almost all other verbs used catenatively, to is syntactically required.
That's all the syntactic background. For the specific context here, You dare not make a mistake is alternative phrasing for the imperative command You must not dare [to] make a mistake - effectively, Don't be so "brave" as to make a mistake (because the consequences would be dire). But of course, what we actually understand from that is...
Don't be so carelessly foolish as to make a mistake!