1. Being a mother is a thankless job, but it's also the most rewarding one.
做母亲是份不值得感激的工作，但同时也是最有回报的工作。

2. He spent years in a thankless job, never receiving any recognition for his hard work.
他在一份毫无回报的工作中度过了多年，从未因他的努力工作而获得任何认可。