This is ultimately what killed my father: 45 years of smoking until one day in 2017 when he quit cold turkey and never picked up another cigarette. By that time the damage had been done. He had severe COPD. He was well passed the point of being a viable lung transplant candidate. He wouldn't survive the surgery. Besides, he already battled a litany of health issues stemming directly from smoking.

Fast forward to last year. His ability to breath normally was already a distant memory, and his ability to breath in any capacity without a struggle had become the new normal. After an evening in the hospital, I picked him and Mum up before a quick detour to the medical supplier in town to pick up... oxygen cylinders and a concentrator. About four months later his condition had deteriorated enough that his GP suggested hospice. A year after this initial but rapid decline and he was gone.

COPD is irreversible. It can be slowed, maybe even halted for a time, but it is impossible to reverse.

I'm glad you quit. You may have quit early enough to maintain a normal life. Regardless, I'm proud of you for taking that important first step.

For anyone else reading this who may be a smoker: Please, I implore you, consider quitting today. I know how the story ends. I've seen it first hand.