Hello. Harmful habits occur when we do not have good self-esteem. If you love yourself, if you want your body (your body is your home), why would you hurt yourself smoking, or doing something else that threatens your health? You have to start from here.
Many people use these bad habits as "pain medicine". Pain is inevitable, choose how to face pain, it is your decision. You decide how to overcome it.
I guess you're aware of the damage you're doing to your body and the people around you (cigarette smoke). So when you want to smoke, you must replace your thoughts in another type of healthier thinking. Example: go for a walk, drink a glass of water, dance, play sports, do something else that diverts your attention so you can make it a healthy habit.