Source: https://eriktorenberg.substack.com/p/nietzsche-on-slave-morality
Nietzsche was worried about this instinct suppression that slave morality enabled. He feared it would lead to the rise of the most despicable kind of person — the /last man/. The last man seeks comfort above all else. The last man no longer understands the value of suffering and chaos and so avoids them. This makes him weak and ineffectual, but the last man calls this “happiness”.
But Nietsche also believed that something was gained in this transition to Slave Morality: /A rich inner-life/. The inner conflict created by the tension between group-beneficial social norms and self-serving instincts drove us to create great art in an attempt to reconcile those tensions. This inner conflict led us to become philosophers, psychologists, novelists, etc. There’s no Woody Allen or Larry David or Dave Sedaris in Master Morality.