How do mortals cultivate to become immortals?

Taoism believes that eating grains will produce foul qi in the body and hinder the path to immortality. Therefore, fasting can be performed. They are the source of desire, and they live on grain energy. If they do not eat grains, they will get rid of the three insects. If ordinary people do not have all kinds of desires, it will be easier for them to realize the truth. Taoism takes cultivating to become an immortal as its goal, and cultivating an immortal is also a process of transforming an ordinary mortal into an immortal. But in life, no one can become an immortal through cultivation.