Lost it over a small matter

This Friday I lost control of myself and had an argument with my manager over taking my lunch in a room where we kept our files.

I was having a busy morning, doing soil tilling, and then had to order lunch from the caterer for the office, and collecting lunch payment for this week.
To add to that, the spreadsheet formula had to be changed due to a different price for one of the lunch item and I was struggling to tally the amount

I was about to have my lunch in the room to have some quiet moment from the hustle when he approached me and said it is not a proper place to eat in the room. He said I could eat at my desk. I said I would like to be alone. I was thinking that my colleague had told him about it and at that moment I was angry that he acted on her "feedback" and not mine when I told him sometimes back that she raised her voice at me and was causing distress with her way of closing the cupboard's doors with some force.

I told him that I cleared the lunch boxes and did not damage anything in the room. I asked him who told him that having meal in the room is not allowed. He said he was the one and appeared offended. Then he told me to ask the CEO if I did not believe and asked him for permission.

I was angry that he was using the CEO's authority on such a minor thing. I  finished my lunch at the desk, thought about that he just brushed it off when I told him about the treatment I received from my colleague who is of the same nationality and said he was bias and why he did not take action but just said because they were stressed out from work.

He later said he is resigning as our department manager, although I apologised to him over the incident, he said his decision is final.

I was thinking about the bad encounters  I experienced and the bad treatment I had received from him and my other colleagues so I lost control and cried.