I mean all is pretty complicated, but it boils down to making the addiction own you.
For some people it’s caffeine, for some it’s pornography, for others it’s nicotine or harder substances. It’s always the same, people lose control of their desires and become a puppet for their addiction. That’s why you know what an addict looks like, and what they act like. Once the addiction takes hold and you stop fighting it, you become its slave.