The idea is that you are doing something out of an urge to do it, but it's no longer fulfilling. What it really is is that the wanting and the liking of whatever you're doing no longer line up. In healthy behaviors, you want what you like, and you like what you want. But when it comes to certain drugs, it's possible to have the wanting and liking come apart.
Where’s the line between an addiction and a bad habit? Why do definitions of mental illnesses change over time? And what’s the most addictive thing in the world?