I was reading a website about smoking cessation which suggested that an indicator of the probability of success is several failed previous attempts.
It makes sense that each time you fail it teaches you about yourself and your weaknesses, my 1st reaction was that if every failed attempt teaches me something then I must be bleeding genius by now but those people that have lapsed recently should take some comfort from the fact that it will assist them on their next quit.
I don't want to suggest that people attempting to quit for 1st time are doomed to failure, however, they can learn a great deal from the imperfections of us old hands!