I remember having to give an hour long interactive presentation to a woman you wore an oxygen mask throughout, within arm's length from me. Every breath was almost a gasp and her emphysema would ensure her constant suffering for the rest of her life.

At that point, 2 years after I had stopped smoking, I really regretted the 10 years of smoking which I only discovered another 10 years after this presentation had destroyed 30 % of my alveoli.

I only developed symptoms of emphysema and asthma 10 years after that discovery. So the 10 years of smoking will likely still get me even though I gave up 35 years ago.