What's "on the brink of" mean?

Native speaker’s answer
Rebecca
Very literally, "the brink" is the edge of the cliff. So, more figuratively, "on the brink of" means to be at a critical or crucial point, or that you're very close to something, and you're just about to experience it, or that it'll happen soon. Ex: I'm on the brink of boredom. When are we leaving the library? Ex: We're on the brink of successfully opening our restaurant!