I really need to get a grip

This is sort of following from my last post, but sometimes I really wish I knew how to properly shut the fuck up.

I was at a Japanese restaurant yesterday with some friends.  It was a group of six and one of them happened to be a huge Japan-junkie, who prettymuch I can easily describe as a weaboo; she claims to be of Japanese descent and know a lot of Japanese (which she does), but ask her to explain something about Japan and why it is what it is, she'll pretend to not hear you or just ignore it altogether.  Fuck, she won't even tell me why her Facebook profile name is in Japanese rather than her English one she was born with and all of us call her by.

That being said, while we were in that restaurant, I was pretty tense because with her with us, I felt like every wrong thing I said or did was taboo or offensive.  I felt expected to eat with chopsticks (Not only use them, but hold them CORRECTLY, a skill I could never figure out.  Seriously, chopsticks need to go fuck themselves.), know how to pronounce the names of the menu items and know basic Japanese customs and body language.

I was a fucking wreck the entire time we were there, and it only worsened when I unwittingly made a comment as of why most Asians were skinny because of how tedious eating with chopsticks was (The restaurant was full of them, most of them happening to be around me when I said it).

As soon as I said it, I wanted to kill myself.  I had disgraced Japan, its people, the Asian countries surrounded by and related to it and most likely made baby Jesus cry.

I spent the rest of the time fretting over it, all the while feeling like a criminal without a shred of dignity left within me.  Hours later while still with two of the people who went with me, they tried to reassure me that no harm was done.  As much as I wanted to play along and believe them, I couldn't.

My problem is this: through my entire life it's been a horrible problem with me forgetting things.  No matter how playful or trivial the potential negative comment I say or am told of is, it stays with me for way too long.  I've found myself losing sleep and forgetting to do work because of it.

I've tried to give as little of a shit as possible, but to no avail.  Why do I still care?  If I didn't, I'd have no problem in solving it.  Unfortunately, my morality always has to think otherwise...