الناس نسيان
The essence of man is forgetfulness. No matter how great or important a memory is, it will slowly disappear even in healthy people. Unless the person is reminded. The antidote of forgetfulness is reminders. That is why we keep albums and photos. That is why we review before finals. That is why we use sticky notes for daily tasks. That is why it is so important to do ibadah, especially the five daily prayers and reading Quran. Ultimately, man also forgets about Allah. All of mankind acknowledged Allah as their Lord before this world, but the majority have forgotten. Even Muslims forget from time to time. Sin and discontent result from this forgetfulness: sin comes when man forgets Allah is watching, and discontent results from forgetting Allah's promise of eternal happiness in the next life. Thus, we constantly need to remind ourselves that Allah is indeed the Lord of everything, that He is watching, that He will judge us. Regular dhikr and ibadah are very effective