What is the ruling on being pessimistic about the number 13, and what should I do to remove the fear of recurring bad events that took place on this day, knowing that everything is decreed and written?

Fear of the number 13 is caused by weakness in faith in Allah's divine decree and destiny, and pessimism is a serious malady. To treat it, one must:

1. Trust in Allah and genuinely rely on Him, cast away obsessions and delusions, and proceed with matters with determination, as the Prophet, peace and blessings be upon him, said: "That is something they find in their hearts, so let it not deter them."

2. Be certain that everything that occurs in the universe is by Allah's decree, as stated in the Hadith of Ibn Abbas: "Know that if the entire nation were to gather to benefit you with something, they would not benefit you except with something Allah has already written for you. And if they were to gather to harm you with something, they would not harm you except with something Allah has already written against you. The pens have been lifted, and the scrolls have dried."

3. Recite the reported supplication: "O Allah, there is no good except Your good, and no bird (omen) except Your bird, and no god other than You."