Quitting was step one. Your lungs are still doing step two.
Your airways are lined with tiny sweepers called cilia. Years of smoke put them to sleep, so the mucus just sits there. That is the morning cough, the phlegm, the heaviness on the stairs.
None of it is willpower. It is a mechanism, and mechanisms can be helped. When you quit, the cilia slowly wake back up, and you can nudge them along, gently, every single morning.

