お得意先が儲かるよう、喜びを感じるように配慮しなければ、やがてお得意先でなくなってしまうだろう。(お得意先)(松下幸之助の言葉から)
If you don't take care of your regular customers so that they would get some profit or feel pleasure, you will lose such customers. (your regular customers)
If you don't take care of your regular customers so that they would get some profit or feel pleasure, you will lose such customers. (your regular customers)