Lose your job?
Argument with a loved one?
Pet death?
New job responsibilities?
Difficult decision to make?
Unexpected bill to pay?
Worrying health symptom?
That's LIFE!
The problem/anxiety/frustration/worry/anger will still be there after that weak moment. It will actually be made worse knowing you have given up a hard earned quit. Take a walk call a friend, take slow/deep breaths, blog "HELP" or just come and read here, write down options, think about the worst outcome and understand it probably won't happen.
Smoking is not required - EVER!