at the mercy of 完全有……支配，任由……摆布
例句：
I'm not going to put myself at the mercy of the bank.
我不想任由银行摆布。
We were at the mercy of the enemy.
我们的命运掌握在敌人手里。
A:Why are you still here? You are supposed to be in the cram school now?
你怎么还在这里？你不是应该在图书馆吗？
B:Because I think it's more meaningful to read some books at home. Come on, this is my life, I don't wanna put myself at the mercy of others.
因为我觉得在家里读书更有意义。这是我的人生，我不想任由别人摆布。