In order to have great happiness you have to have great pain and unhappiness - otherwise how would you know when you're happy?
When you are skinning your customers, you should leave some skin on to heal, so that you can skin them again.
He told me he was working as an interpreter in a doctor's office in Brookline, Massachusetts, where I was living at the time, and he was translating for a doctor who had a number of Russian patients. On my way home, after running into him, I just heard this phrase in my head.