This might include anticipation of drug use, during a binge, withdrawal, feelings that persist after abstinence, and changes from their emotions before initiating drug use...
Dealing with anykind of drug addiction the emotions will traverse thourgh the entire spectrum. It is so hard to predict behaviors and emotions when dealing with addiction because it is really an inherent process of the addicted. Although there are many traits shared amongst drug addiction and the withdrawl thereof. These usually include: agitation, irritablity, fatique, sleeplessness, nausea, diarhea/dehydration
Some even refer to the withdrawl process as an emotional rollercoaster. Hope this helps you in the quest for your answer.
I agree with Steven. You may also want to consider that people in treatment often have a poor understanding or awareness of their emotions in general, which is often associated with poor ability to regulate them (i.e., how can you try to control something you don't understand?). E.g., http://www.sciencedirect.com/science/article/pii/S0376871606004881
In addition to the comments of Steven and Kevin above, keep in mind that "patients" (ambivalent or engaed) may have additional considerations in their perception of drug use as opposed to users not seeking out treatment.
Thank you all for the answers you have provided. If anyone has any anecdotes about the feelings the surround the actual use of the drug, I would be very interested. Kevin, I love the Fox et al. article that you had posted. I was familiar with the article before your posting, and constantly look back to the paper. Again, thanks everyone!