Beside Yourself was created in 2004.

Imagine that you have so much emotion that you need two bodies to contain them. That's what the image for this idiom is -- you're "beside yourself" with extreme emotion, such as anger or grief.
To be 'beside yourself' means that you aren't behaving as you normally do. For exapmle, to be 'beside yourself' with grief means that you are overcome with mourning and it is affecting your actions.

no one know beside my teacher

Feeling all beside yourself! Feeling like you burned someone

To be beside yourself means to be overwhelmed with emotions, usually negative ones such as anger, frustration, or disbelief. It suggests a feeling of being unable to control or cope with the intensity of what one is experiencing.