When you lose the both sides.
(Consider this literally translated Idiom: "I'm now a two-heads-burned wood.")
I don't mean lose-lose situation.
It's the antithesis of "hitting two targets with one bullet" (I know I'm wrong in saying this one too).
E.g. (for the original question) one of your friends asks you a favor, parallel another friend asks you another favor. If you choose to help only one of them, any, you will do it for sure. Now you choose to help both, then you become unsuccessful on both, and now they're chagrined of you.
Now, after this failure on both sides, you call yourself "I'm a two-heads-burned wood."
No, it's not the duplicate of what Tymek said.
