https://www.sciencedaily.com/releases/2018/07/180705113938.htm

New findings published today in the Journal of Substance Use suggest that smokers who have quit often relapse because they want to recapture a sense of lost social identity. And that many ex-smokers experience quitting as a 'loss'.

As well as being physically addictive, smoking has a range of emotional, behavioural and social triggers.