How can I increase patience and endurance regarding divine decrees without opposing God's will, and is the saying, "O God, I do not ask You to avert the decree, but I ask for leniency within it," forbidden?

He who strives for patience will be granted it by Allah, as is the case with all acquired virtues such as knowledge and forbearance. One can train their soul to be patient by undertaking voluntary actions that require steadfastness. Patience increases with the strengthening of faith and trust in Allah's divine decree and destiny. The knowledge that "what has befallen you was not going to miss you, and what has missed you was not going to befall you," and that "victory comes with patience," increases one's endurance. Furthermore, knowing the reward of the patient and contemplating the stories of the prophets and righteous people also increases patience. As for the saying: "O Allah, I do not ask You to avert the decree, but I ask You for gentleness in it," it is not a Hadith, and prominent scholars have warned against it because it contains ill-manners towards Allah and contradicts the meaning of the Hadith: "Nothing repels the divine decree except supplication."