I need support quit smoking, but cheated today?

Not a Failure. There will be stumbling blocks along the way. Most studies suggest not trying to quit all at once but gradually as you use all the aids available to you, including enrolling in smoking cessation program. It is a chemical addiction/dependence and didn't get that way overnight so the urge will not go away overnight. Important point is to want to quit, have plan and work toward completing the plan.