After quitting smoking, since the irritation of smoke on the lungs and airways stops, the lungs begin to rejuvenate and will expel outward some of the dirt and garbage deposited in the lungs from previous smoking, so this is a good sign. Because there is this effect of expelling phlegm, it means that most of the lungs have not been damaged by the smoke and have the vitality to restore self-help. You should try to use phlegm-removing medicine to help get the dirty phlegm out of the lungs, and the more black phlegm that is expelled, the less garbage will remain in the lungs. Never remember not to stop coughing, because once you stop coughing this phlegm will not come out, and the best chance of self-healing will be lost, and you must encourage phlegm excretion. You can do more physical activities that allow you to catch your breath, such as playing or climbing, swimming, or running, because effective breathing movements can help the phlegm to be expelled more fully.