What worked for me, was to have one solid reason for giving up, that if I was starting to feel like I might start smoking again, I just said to myself "do you want that cigarette or do you want....". It worked. It has to be something you really really want, that you cannot have if you smoke. And not something general or too sensible like to want to be healthier. For me, it was having a baby. So if I ever started to think about smoking again I would say to myself "do you want a ciggie or a baby". Is there something you would love to save up for, something you have always wanted, maybe a holiday of a lifetime or a new exciting hobby? You could use money saved from smoking to pay for it.
I also changed my routine, and planned what to do for parts of the day that I knew would be harder. For example, I used to smoke as soon as I got up in the morning, and always enjoyed that first smoke of the day. Instead I brought a book with daily readings and would read that each day with a cuppa. It gave me another focus.
I also had a nicorette inhalator which I hardly used, but liked to have as a safety net, and it was something to hold. On the box it came in, it gave me access to an online thing you could do. You signed up and it gave daily support and exercises to do. I found it very helpful and kept my focus.
Reframe it positively in your mind: you are not giving up, you are stopping smoking. You are not in the middle of a process, you are now a non- smoker. These small changes to how you see it make a difference to your state of mind.
I smoked 20-30 day and have not smoked a single cigarette for 7 and a half years now. I think preparation is key. Think in advance about why you are doing this. And about what you anticipate to be the most difficult times and plan for these.
Good on you for stopping. I still feel proud for stopping smoking and I am sure you can do it too.