What does Beside myself mean?

Beside myself meaning in Urban Dictionary

severe pleasure, anger, an such like, due to a scenario that triggers anyone to be "out of the mind" thereupon feeling."Beside" was formerly (15th through 19th hundreds of years) used in expressions to imply "out of a mental state or problem, as 'beside an individual's patience, an individual's gravity, a person's wits'" (Oxford Engl. Dict.), which usage survives just in "'beside oneself': out of an individual's wits, out of one's senses."