Negative emotions are necessary and useful?


I am in the process of creating my business and I feel fear created by various thoughts.
I don’t understand how fear can be useful and can be necessary:
Indeed, Brooke says that negative emotions are necessary but I do not understand in which way there are necessary in this process of creating my business?
My actions from feeling fear are wanted to quit and hide.

Same question: in what ways, in my C, negative feelings like Fear could be useful for me?