No luck finding your quote. Here's a little something that comes sort of close:
Most smokers try to quit, and fail, several times before succeeding. There's some evidence that the more times a smoker has tried and failed to quit, the better the chance of success the next time.
http://www.gaspforair.org/gedc/gedccons.htm
http://www.assumption.edu/users/lknoles/habits.html