That is because “Sleep is the brother of death.”-Prophet Muhammad (SWS)
By forgetting things, you become ignorant. They say ignorance is bliss. It is blissful for those who lose themselves. It is blissful because they forget the pain and fail to acknowledge the truth. They don’t face their internal demons and they let ignorance grow in their hearts.
By blocking out the truth, you numb out the impending reality. By becoming numb, you become ignorant. By becoming ignorant, you ask for dire consequences. Stupidity is not only a symptom, but a choice. You choose to lower yourself to the level of ignorance you are in. By becoming stupid, you close off open-mindedness. You fixate on one target and force yourself to focus on that one thing, rather than other, healthy possibilities. The mind kills the other sound, making it white noise.
The Prophet Muhammad (SWS) said that one who wakes up has a veil over his heart. This indicates that sleep causes ignorance. Through sleep, one is forgetting and enjoying its bliss; this does not mean, however, that sleep is evil in anyway—it is necessary, but a paradoxical feature of nature. It causes ignorance, but we need it to live. Thus is the paradox of sleep.
In the same way, people block out the reality before them. That reality is not of this life, but the next. People block out the fact that there is a Heaven and Hell, and that they will be judged according to the best of their deeds whether they will go to one or the other.
“And they say: "The Fire shall not touch us but for a few numbered days:" Say: "Have ye taken a promise from Allah, for He never breaks His promise? or is it that ye say of Allah what ye do not know?"
Nay, those who seek gain in evil, and are girt round by their sins,- they are companions of the Fire: Therein shall they abide (For ever).
But those who have faith and work righteousness, they are companions of the Garden: Therein shall they abide (For ever).” (Qu’ran 2:80-82)
Pleasure can in a way cause ignorance. Pleasure is necessary for moderation, but can be overwhelming in excess. Overwhelming pleasure is evil. Enjoying something too much can lead to addiction, which leads to obeying the addiction and creating a veil of ignorance. The way to kill that pleasure is not too hard at all: remembrance of the greater sleep, death.
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said, “Remember often the destroyer of pleasures,” by which he meant death.
By remembering death, one will stop caring about the temporary pleasures of this world. But one should do so in moderation, not giving up everything at once. One should try to balance himself with this world and next, fearing Allah, but not death. Death is a thing to remember in order to rid oneself of his temporary, and often sinful desires.
Similar to death is sleep. It is the brother of death. In a way we die every night, and if Allah wills it, we are returned to our bodies, rejuvenated once again. But people do die in their sleep. May Allah grant them forgiveness, and us forgiveness if we are ever to die that way, or any way.
“And it is He who takes your souls by night and knows what you have committed by day. Then He revives you therein that a specified term may be fulfilled. Then to Him will be your return; then He will inform you about what you used to do.” (Qu’ran 6:60)