Is it permissible to supplicate for a fatal illness?

"My advice is to occupy your mind with beneficial interests and lofty matters, and to wish for the betterment of this world and the Hereafter. This is supported by the hadith: 'When one of you wishes, let him wish for much, for he is only asking his Lord.' And there is a prohibition against wishing for death, as stated in the hadith: 'Let none of you wish for death due to a hardship that has befallen him. If he must do so, then let him say: O Allah, keep me alive as long as life is better for me, and cause me to die when death is better for me.' There is also a prohibition against wishing to encounter the enemy, as the Prophet (peace be upon him) said: 'Do not wish to encounter the enemy, but ask Allah for well-being. If you do encounter them, then be patient.' And beware that illness can hinder one from doing good, exhaust one's strength, and may lead to discontent or disbelief."