Welcome,
Your confidence should be rooted in your knowledge of your addiction. What else could you point to that will otherwise make this time different than aall the others. Whyquit.com and this forum offer a unique perspective on addiction - we encourage you to quit nicotine not just smoking. We want to impress upon you that you are addicted to nicotine not to smoking. The sadness you feel is related to the physical addiction and the psychological associations deeply ingrained in your daily routines associated with administration the drug. To be a successful ex-smoker you should learn as much as you can about your addiction to nicotine because the more you know, the less likely you are to relapse.
Here are a few recommendations for reading but the one and only rule you must remember is the maxim that we all live by. Never take another puff. What everyone who has quit and relapsed must take from that experience is that in order to quit smoking you have to quit smoking. In order to remain free you must never take another puff.