5301991f_and_The_Art_of_Breaking_Things__detailed_explanation
[signal] Smoking [part of body] mouth [possible meaning(s)] self-comforting [detailed explanation] 
Smoking obviously becomes habitual and addictive, but aside from this people put things into their mouths because it’s comforting like thumb-sucking is to a child, in turn rooted in baby experiences of feeding and especially breastfeeding.
“I pretty much try to stay in a constant state of confusion just because of the expression it leaves on my face.” – Johnny Depp | Zen and The Art of Breaking Things
detailed explanation