'You thought you'd never shed a tear So this must astound and must confound you' seems like the all is lost moment for the protagonist's friend. He's finally hit rock bottom after having become a drug addict, and the protagonist uses his chance to try and talk sense into his friend. He's understanding of how quickly someone can get addicted to that stuff and he reveals to his friend the ending of where drug abuse leads to: to death.
'You thought you'd never shed a tear So this must astound and must confound you' seems like the all is lost moment for the protagonist's friend. He's finally hit rock bottom after having become a drug addict, and the protagonist uses his chance to try and talk sense into his friend. He's understanding of how quickly someone can get addicted to that stuff and he reveals to his friend the ending of where drug abuse leads to: to death.