I usually suggest people spend some time reading on the substance abuse forum... what I usually see is people struggling in various ways to abstain from substances, or figure out how they can life life without a crutch.. many talk about concerns for their families, their children, or careers, how disappointed they are in themselves...
We have been doing a book review, and part of it is examining the effects of drug abuse.. and while different substances have different impact.. drugs in general affect the dopamine in the brain.. the happy feelings we have.. or the inability to feel happy.. drugs affect the prefrontal cortex where we assess risks and weigh consequences.. and the limbic system is also affected... where we are left feeling there is a sense of urgency and panic, etc.... all of these physical symptoms come into play at different times and affect how a person thinks and feels..