A couch potato:沙发土豆(整天窝在沙发里看电视的人);电视迷
His mother always warned him he'd turn into a couch potato if he watched too much TV.
他的母亲总是警告他说要是看太多电视会变成沙发土豆的.

Run/take its course:(of a series of events, an illness, etc.) develop in the natural or usual way without being chanded or stopped.
(指一系列事件或疾病等)持续到自然结束,任其发展,听其自然
The doctors agreed to let the illness run its course, rather than prescribe drugs which had little chance of success.
医生认同此病只能顺其自然,而不用那些几乎没有什么疗效的药.
We must allow justice to take its course.
我们必须让正义得到伸张.