salam
45:23 has also the same statement ! I think ALLAH talks about people who always follow their inner desires not matter what. Those who don't think about punishment, justice, heaven, hell, rejecting the will of the Creator, but always follow worldly things they want to get! (worldly desires) So they become "slaves" of their instincts. Perhaps their motto is like "do whatever you dream of! whatever you want! no one is more important than yourself! this is you and your life! What really matters is you ! Break the rules and enjoy life! Nothing can hold you back! etc."
May ALLAH (swt) protect us all from being one of those who are slaves of their instincts and desires ! (ameen)