Mouse tail juice means to take care of yourself. It comes from master Ma Baoguo, the leader of Hunyuan Xingyi Taiji sect. On May 17, 2020, Ma Baoguo, 69, was knocked down three times during a duel with Wang Qingmin, a folk martial artist and 50 year old fighting coach. Finally, he was KO. This is a famous event of Ma Baoguo.
The so-called "mouse tail juice" is a homonym. It has the same meaning, but it has a lot of fun than the idiom. Ma Baoguo, a 69 year old "Tai Chi Master", threatened to correct the name of traditional martial arts in the afternoon against Wang Qingmin, a 49 year old folk boxer. He was finally Ko by the folk boxer for 30 seconds. Afterwards, Ma Baoguo sent a video accusing Wang Qingmin, in which he said the famous saying "mouse tail juice".
Now many friends use "mouse tail juice" instead of "do it yourself". Generally, it means more to blame yourself. "Mouse tail juice" is just the opposite and belongs to ridicule.