If you have already been diagnosed with COPD, asthma, or another lung condition, quitting can start to feel like closing the barn door after the horse has left. The damage, or so the thinking goes, is already done, so what is the point now? That fatalism is understandable, and it is also not true. Lung conditions can still get measurably worse with continued smoking, and quitting - even after a diagnosis - is one of the few things shown to slow that decline. The point is not to undo the past. It is to protect however much capacity you have left, starting today.
The first weeks after quitting can also be genuinely confusing if you already have a lung condition, because withdrawal brings its own cough. Airways that were coated and numbed by smoke for years start clearing themselves out once the irritation stops, and that cleanup often shows up as more coughing, not less, in the short term. If you also have COPD or asthma, it can be hard to tell whether that is normal withdrawal cleanup or a flare-up of the underlying condition, and that uncertainty alone makes some people reach for a cigarette to make the coughing "calm down," which only restarts the cycle.
This is exactly the situation where looping in your doctor or pulmonologist before you quit, not after, makes a real difference. They can help you tell the difference between expected withdrawal cough and something that needs attention, and they may adjust inhalers or medication timing to make the first weeks steadier. Quitting with a lung condition is not something you have to figure out entirely on your own.
There is also an emotional weight that comes with a diagnosis like this, a sense that smoking has already "won" and quitting now is just closing the barn door. It has not won. Every additional cigarette on top of an existing condition adds real, avoidable strain. Quitting now does not erase the diagnosis, but it does change what happens from here, and that is the only part actually still in your control.