Is it permissible to supplicate for death before relatives and loved ones, out of fear of the pain of their separation, knowing that there is no depression or pessimism involved?

It is not permissible to wish for death due to a worldly harm that has occurred, so how about an expected harm that has not yet occurred? This is based on the Hadith of Anas ibn Malik: "None of you should wish for death due to a harm that has befallen him. If he must do so, let him say: 'O Allah, keep me alive as long as life is better for me, and cause me to die if death is better for me.'" The Salaf interpreted the harm mentioned in the Hadith as worldly harm.

This life is a realm of trial and tribulation. Allah tests His servants with adversity and prosperity, as stated in His noble verse: "And We will surely test you with something of fear and hunger and a loss of wealth and lives and fruits, but give good tidings to the patient." And His saying: "You will surely be tested in your possessions and yourselves. And you will surely hear from those who were given the Scripture before you and from those who associate others with Allah much abuse. But if you are patient and fear Allah - indeed, that is of the matters [requiring] determination." Therefore, a Muslim must accustom himself to patience concerning Allah's decrees.