1. What does it mean?
중꺾그마 playfully revises 중꺾마: the important thing is continuing even after feeling discouraged. The expression is associated with comedian Park Myung-soo and his variation on the idea of an unbroken spirit.
Also written or said as jungkkeokgeuma
2. The nuance
Its humor admits that people do feel defeated instead of demanding constant confidence. It can encourage a modest next step, but should not be used to pressure an exhausted person.
3. Examples
“마음은 이미 꺾였지만 한 줄 더 썼어. 중꺾그마지.”
I was already discouraged, but I wrote one more line. That's carrying on anyway.
“완벽한 의욕은 없어도 중꺾그마 마음으로 연습했어.”
I practiced with a 'keep going anyway' attitude, even without perfect motivation.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.