What is the ruling on someone who knows what is right but cannot follow it because they are accustomed to error and find it difficult to abandon?

Accepting the truth is a great virtue, while insisting on falsehood—despite the clarity of truth—is a vile sin, and it is the behavior of Iblis (Satan), as Allah Almighty says: "Woe to every sinful liar. Who hears the verses of Allah recited to him, then persists arrogantly as if he had not heard them. So give him tidings of a painful punishment" (Quran 45:7-8). And the Prophet, peace and blessings be upon him, said: "Whoever disputes in falsehood while knowing it, remains in Allah's displeasure until he refrains."

Therefore, persisting in falsehood incurs Allah's wrath. A Muslim must not belittle his mistake or sin, for a believer sees his sins as if he were at the base of a mountain, fearing it might fall upon him, whereas a wicked person sees his sins as a fly that passed over his nose.