How much of "anxiety" is a healthy thing?

Since I learned about the word I think I misinterpreted it as something exclusively bad for oneself. Recently I've read in a psychology book a small passage that was about how anxiety is not solely a way of giving a message of fear but that actually it is a necessary feeling for having a healthy psyche, and that the body's objective is not to lack it but to sustain a moderate ammount of it.

That said, and connecting the subject to social anxiety, how much of this awareness is healthy? How much do you think it is needed?

I ask because I think that I could be taking some anxiety and interpreting it as bad or harmful when maybe it is altogheter normal, even if it is somewhat energy draining.