Definition
If something difficult, unpleasant, or strange is considered normal or routine for someone, it is regarded as an ordinary part of their job or life.
分内工作（本份事情）
For firefighters, risking their lives to rush into burning buildings is all in a day's work.
对消防员来说，冒着生命危险冲进燃烧的建筑物是家常便饭。
Seeing blood during surgery is all in a day's work for a doctor.
在手术中看到血对医生来说是家常便饭。
Handling large quantities of ingredients during meal preparation is all in a day's work for a professional chef.
在准备餐点时处理大量食材对专业厨师来说是家常便饭。