Your stomach sinks, you have that sinking feeling in the pit of your stomach, when you get a bad grade on a test.

当你考试考砸的时候,你的胃会垂下去,或者说,会有胃部下垂的感觉

耶鲁公开课 - 死亡课程节选

And you're feeling like you're in a light mood. You've just passed a test.

但你觉得你想看点轻松的，因为你刚刚通过一门考试。

I feel like 课堂 - SpeakingMax英语口语达人