bite 就是咬；chew 是嚼，bite off more than one can chew如果一口咬得太多，那就嚼不了了，即不自量力；贪多嚼不烂；承担力所不能及的事；心有余而力不足。

【例句】
Listen son, you have a lot of responsibilities already. Are you sure you can manage football and your studies and your job? Be careful you don't bite off more than you can chew.
儿子，听着，你已经有许多事情要做的。现在你要参加学校的美式足球队，你还要学习，再加上打工，你肯定能安排好那么多事吗？你得小心，不要不自量力。

By accepting two part-time jobs, he is clearly biting off more than he can chew.
通过接受两份兼职工作，他显然是承担力所不能及的事。