You're playing tennis with your boss for the first time. You're winning and your boss is getting angry. Do you let him win? Hahahahaha...I doubt I would ever be beating anyone in tennis, but I get the gist. I think I would. It reminds me of that Friends episode where Chandler and Monica are playing tennis with his boss. It's not that important to me to beat someone. So, I am pretty sure that I would just let my boss win.
A murderer tells you where the body is buried. You're his lawyer and this evidence will certainly convict him. But the victim's family needs to know the truth. Do you keep silent? Ah. Well, I was pre-law for a while, and you can't divulge your client's secrets. Even if you don't get disbarred, I am pretty sure nobody would want you for a lawyer anymore. So, no, of course I would not say anything.
You're divorcing and must split your assets with your ex. S/he doesn't know the true extent of your wealth. Do you disclose it? Heh, especially since I am a girl, I would keep it to myself. Besides, if I was getting divorced it would have to be something major, like he was abusive, or cheating. So the slimeball would deserve it.