What is the ruling on invoking disbelief upon oneself or wishing for one's deeds not to be accepted? And is the repentance of someone suffering from obsessive-compulsive disorder accepted in this case, and how does he repent?

It is not permissible to invoke worldly calamities upon oneself, so how can it be permissible to invoke death upon disbelief? However, it is not considered apostasy, according to the more correct opinion, if the intention was merely to supplicate and not to embrace disbelief. Rather, it is a voluntary sin. A person overcome by obsessive whispers (waswas) is excused for it. Whoever says, "May Allah cause him to die a disbeliever," whether to himself or to another, does not become a disbeliever by that, because his intention is to insult, not to desire disbelief. One must stop this supplication and turn away from obsessive whispers. Repentance erases what came before it, and Allah forgives all sins. A supplication against oneself might coincide with a time of answered prayers, and thus be answered. However, a person's supplication against himself in anger might be considered idle talk for which there is no accountability, and it might not be answered as a mercy from Allah.