Why did I quit my last job?

Because I found it difficult to strike a balance between learning English and doing my work.
Even though I could take a rest on Monday, I still had to do the rest of my work.
As a recruit I had to work about 12 hours every single day from 9 to 9 or from 10 to 10 because our center was the newest one at the time (my tasks were: uploading photos and giving descriptions of them, communicating with parents, having meetings etc.).
Although I was seldom a co-teacher in S1, I felt my English was dying because I kept on giving lower-level lessons.