Seek support from your family, friends and doctor. Don't tell yourself that smoking one cigarette now and then is okay. In terms of your health, even one or two cigarettes aren't safe. People who smoke one or two cigarettes a day are more likely to return to their previous level of smoking after a brief period of time. If you do start smoking again, don't give up.
Many smokers try to quit several times before they succeed.
Try to understand what made you start smoking again, go over your reasons for quitting, and try again.