The second major idea is that drug use is a habit that becomes harmful. It is always very hard to stop bad habits, but in this idea, drugs are one of the strongest bad habits because drugs cause so many changes in the brain. Each time a person uses drugs, the parts of the brain that think about drugs become stronger and stronger. In this idea, if a person likes drugs, that person starts to plan their day around using drugs. To stop a habit as strong as drug use, many other things about that person's life must also change. This idea also means that, the longer a person takes drugs, the harder it is for them to stop taking drugs. 