What is the supplication, action, or solution to get rid of the constant fear of losing one's mother, which causes insomnia and crying, and is the supplication "O Allah, I seek refuge in You from the cessation of Your blessing, the change of Your well-being, the suddenness of Your vengeance, and all Your displeasure" sufficient to reassure the heart?

Fear of death is unwarranted, harmful, and brings no benefit, for what Allah has decreed will inevitably come to pass, having been written fifty thousand years before the creation of the world. What is obligatory is to have a good opinion of Allah and to entrust all matters to Him, for all of Allah's decrees are mercy and wisdom, and He is more merciful to us and more knowledgeable of our best interests. The believer does not attach his heart to this world, knowing its transient nature. "Live as you wish, for you are destined to die; love whom you wish, for you are destined to depart from them; and do as you wish, for you are destined to meet its consequence." When a believer comprehends the true nature of this world, he lives a good life and benefits from both its sweetness and bitterness. "Wondrous is the affair of the believer, for all his affairs are good... If something good befalls him, he gives thanks, and that is good for him; and if something bad befalls him, he shows patience, and that is good for him." Fears overcome a weak heart, whereas a strong heart connected to Allah is in security and tranquility, for true faith bestows serenity, reassurance, and optimism. Strengthening the heart is achieved by purifying it from doubts and sins, and by nourishing it with remembrance of Allah, knowledge, and worship.