"Go on - but don't think you can kill my confidence. I've had experts doing it for years"

In this quote, John Osborne is revealing his strength and decision in the face of criticism and doubt from others. He is essentially saying that he will not let anybody or anything damage his confidence, as he has currently sustained years of professionals attempting to do so. This might be interpreted as a declaration of defiance and self-assurance, as Osborne declines to let others dictate his self-regard. It likewise speaks with the idea that confidence is something that must be cultivated and secured, as it can easily be chipped away by negative impacts. In general, this quote showcases Osborne's strong sense of self and his refusal to be broken by outside forces.