S-7:set one's jaw 坚持到底
A:I haven't seen you for a long time. What are you doing?
A:好久不见了，你在干什么？
B:I've been keeping on studying the piano.
B：我一直在学弹钢琴。
A:How's it going?
A:学得怎么样？
B:Too bad. I failed the test for degree. So I have to set my jaw to do more practice.
B：糟透了，我等级考试没过，所以我只好咬紧牙关进行更多的练习。
