The fact that I owe you money is entirely beside the point.
3 beside oneself. out of one's mind or wits, at the end of one's tether, overwrought, agitated, upset, crazy, mad:
She was beside herself with grief when she heard the news.
Advanced English Dictionary
preposition 1 next to or at the side of sb/sth: He sat beside her all night. + a mill beside a stream 2 compared with sb/sth: My painting looks childish beside yours. Idioms: beside yourself (with sth) unable to control yourself because of the strength of emotion you are feeling: He was beside himself with rage when I told him what I had done. + They were beside themselves with excitement. WHICH WORD? beside / besides The preposition beside usually means 'next to something/somebody' or 'at the side of something/somebody': Sit here beside me. Besides means 'in addition to something': What other sports do you play besides hockey? Do not use beside with this meaning. The adverb besides is not usually used on its own with the same meaning as the preposition. It is mainly used to give another reason or argument for something: I don't think I'll come on Saturday. I have a lot of work to do. Besides, I don't really like parties. +She likes football. Besides, she likes tennis and basketball.
Random quote: The conditions of conquest are always easy. We have but to toil awhile, endure awhile, believe always, and never turn back.: Seneca