Does cursing oneself and grumbling erase the blessings of one's life and provision, and is it considered a bad assumption about Allah?

A Muslim cursing themselves is a grave error that could be a cause for evil to befall them, and it indicates a poor opinion of Allah and a lack of contentment with His decree. The Prophet, peace and blessings be upon him, forbade supplicating against oneself and condemned cursing. Therefore, one must repent to Allah, have a good opinion of Him, be patient in the face of calamities, and submit to Allah's judgment.