In the case of humans...
In the case of humans, they are a result of the interactions of his heart and his lower nafs. The less involved is his nafs, the more involved is his heart. Looking further inward, there is the ruh. If one's nafs has been burnt away, then his heart is active and pulsating; it is then fed by the spring of comfort - the ruh, the spirit. Those who are not in submission rebel against the fact that they are perishing.
If you tell someone that he is aging and that his teeth are falling out, he will say that he is not yet old or ready to die. Everyone considers his age as the average. When you were twelve years old, you thought fifty was ancient. You could not communicate with fifty year-olds, they were funny people. But when you became fifty, you thought fifty was quite young. This is because there is in man an echo of the Everlasting. But there is also in man an echo of the nafs of rebellion.
He assumes that the nafs lasts forever, and does not remember death. The seeker is repeatedly given the advice by his masters that the most potent medicine for ailments of the spirit is the remembrance of death. It is not used to paralyze man or to make him inactive and negative but, on the contrary, it is used to make him successful in his actions by making him more efficient.
If he constantly remembers death, his actions will be pure, untarnished by his personal greed, arrogance, vanity, revenge and whatever other attributes are characteristic of the lower self. The face of the Lord is, at first, an existential connection between man and Reality. Man wants to be healthy, he wants to be in the company of fine men, he wants to be in an environment that will help him get deeper into the knowledge of Reality, of which there is no end.
The more one knows Allah, the greater is the desire to know more of Allah. One should not assume that once somebody knows Allah that is the end of it. There is no beginning or end to Reality. An arif bi-llah is one who has had a window open onto Reality. The more he is able to look out from that window, the more he will see of Reality. Just as each human has a physical birth, so too does each one have a spiritual awakening, which takes place parallel in time.
Just as man was physically once a child, so too was he a child in knowledge of Allah.. There is no end to Reality, because It encompasses before and after creation.