Say, you are working for a bad boss who treats you badly. However, you don't dare to do anything to upset him but sneakily apply for a new job and wait until you get a new job offer.
When you get a new job offer, you can shout at him or sat bad words to him to ease your anger. You don't care if he sacks you or not because you ve got a new job offer.
Another example, in a family, a person treats his/her spouse badly, but the spouse doesn't fight back but wait until the right moment to fight back.
Do we have an expression saying that a person is in a bad situation but doesn't dare to fight back but wait until the right moment?
For example, "he bit the bullet and wait for the right moment to fight back"