If a Muslim continues abandoning the Quran in his life, the faith in his heart begins to weaken, he becomes accustomed to disregarding Allah’s commands, and he begins to forget about Allah’s promise in the Hereafter, and instead, desires the pleasures of this life.
The connection with Allah سبحانه و تعالى, that gives true life to the hearts of humans, becomes severed and the heart becomes a dark dungeon; the filth of sins veils it and no light of guidance penetrates it.
This is why Uthman bin Affan رضي الله عنه said: “If our hearts were really clean, we would never became satisfied with the words of Allah.”