In a nonpsychotic person, the subconscious tries to protect the person and even gives advice during dreams. This appears to especially be the case with drugs. I have never seen a situation where the dream showed approval for hard drug abuse.
A 28-year-old woman dreamed that she was spitting out shards of glass. Crystal meth is sometimes called “glass.” She recently was trying to detox herself from crystal meth. Spit is a form of water. Water almost always represents emotion.
The act of spitting indicates that the person needs to expel something from the body. The dream was advising her to throw crystal meth out of her body. The dream especially emphasized the negative effect crystal meth was having on her emotions.
** See how dreams are psychologically interpreted in Dreams: Guide to the Soul at http://www.drstevenfox.com