My girlfriend always said she did it because it was pleasant to her and she enjoyed it too much to stop - as in, the pleasure in the now was more important to her than potential future complications. She'd regularly smoked for 8 years (1/4 to 2 packets a day). Then we started talking about moving in together and after some misunderstandings and minor rows, she gave up on it. Which makes me feel like oh so proud and loved lol. After the period of no smoking, she now coughs at trying to and the cigs are not pleasant to her palate, so I guess she may have just left them for good...