If you can adjust mentally to consider yourself as a non-smoker and feel pleased with yourself rather than as someone trying to give up smoking it makes a massive difference. So you became a non-smoker 3 days ago. Well done.
Ex-smokers start again. Non-smokers don't. It's a state of mind.
A little information.
There are 2 types of cigarette.
Type 1 is the one that maintains the nicotine level in your bloodstream. You need 6 a day as a smoker. After 18-24 hours of not smoking, you have gone past the satge where lack of these cigarettes matters. You are no longer chemically addicted after that.
Type 2 is the hard type to give up. They are the trigger/habit cigarettes you didn't even notice lighting up. The phone rings - miraculously you have a lit cigarette moments later. You sip a coffee and a cigarette appears in your hand. These are the cigarettes you actually have a problem giving up, but they're actually not the ones you thought you were addicted to.
Strategies for type 2 cigarettes.
First avoid as many of these triggers as possible. That means giving up coffee/beer or any other triggers you have for a couple of weeks.
Secondly, every time the phone rings or you get in a car ( or whatever your trigger points are) and you have that momentary thought to get a cigarette, just think 'I don't smoke and I'm glad' then deliberately concentrate on whatever your actually doing. If nothing else, this will improve your driving and your phone conversations.
Thirdly, Just stop thinking about smoking. You aren't a smoker so stop thinking about it. I never, ever think about shooting up. Why? I'm not a heroin addict. If I had a momentary thought about shooting up I'd simply shrug it off. Do the same with smoking.
Fourthly. If you can ally becoming a non-smoker with other positive lifestyle choices so much the better. When I gave up I also dieted and joined a gym. That is to say I went on a health kick which made smoking non-commensurate with my lifestyle. Feling better about yourself and your fitness is a strong motivator.
Fifthly. If you used to smoke at home, dry clean your soft furnishings. Your sub-conscious mind is very aware of trace smells of smoking so you may sometimes feel like a cigarette without knowing why. It will be because there is a faint odour in the room. Avoid other smokers, whether they are smoking or not, for the same reason. The smell on their clothing can make you crave a cigarette without knowing why.