The second adverse consequence of committing sins is that in a Hadith the Holy Prophet ﷺ said that when a person commits sin for the first time a dark spot is placed on his heart. What is the reality of that dark spot, only Allah Ta’alah knows best. When he commits a second sin, a second dark spot is placed on his heart, and after a third sin a third spot is placed. If he then commits Taubah (repentance) then all these dark spots are erased. But if he doesn’t perform repentance and keeps committing sins, those dark spots eventually cover his whole heart. Then those dark spots change into rust and his heart becomes rusty. Once his heart becomes rusty, he loses the ability to accept the truth. He then becomes so misguided that he becomes unable to recognize sins as sins and stops seeing the adverse consequences of sins.