When you say that something is for your own good it can mean something that is for the benefit of oneself. If for example, you state that someone is too nice or too clever for their own good you mean that their quality may, in fact, be a disadvantage rather than an advantage.

1. Your marriage is over. You need to forget about your ex-wife and move on. I'm not saying that to hurt you, I'm saying it for your own good.
2. I know you would like to have ice cream for breakfast but I'm not going to let you for your own good.
3. You shouldn't have lent that money to Paul. You are too trustworthy for your own good.

1. You look so stressed at the moment. For your own good I think you should take some time off work and unwind.
2. Jack is too cocky for his own good. He will never get ahead in this business with an attitude like that.