Mark is a heroin addict who always shoots heroin in his apartment. One day Mark goes to a different city, injects heroin in his hotel room and overdoses. Why did Mark overdose?

Heroin is the addictive drug prepared from the morphine that are obtained from the poppy plants. The heroin can be directly inhaled and causes the intense feeling of relax.

The individual that suffers from tension or any other problem and wants the intense feeling takes the heroin. The Mark directly the heroin in her blood vessels and taken extra amount of drug that reduces her all tension. The excess intake of heroin leads to its over dose.  

the trait of personality falls in the middle of the diagram because personality is a mixture of ones nature and environment.