How is a sudden death a relief for the believer, and is it true that not everything that afflicts a believer and is patiently endured expiates his sins?

Scholars have differed on the authenticity of the hadith narrated by Aisha, may Allah be pleased with her, regarding sudden death: "a comfort for the believer and a regrettable seizure for the wicked." Some have authenticated it, while others have weakened it. It is also narrated in a hadith by Abu Dawud, "Sudden death is a regrettable seizure," which was authenticated by Al-Nawawi and Al-Albani. The people of knowledge have reconciled between these hadiths by explaining that sudden death is a comfort for the righteous believers, while for the heedless, it is feared to be a regrettable seizure for them, as they did not repent.