枉费心机

枉费心机[力] [wǎng fèi xīn jī]

1. ■ rack one's brains in vain; be an ass [a fool] for one's pains; contrivances; flog a dead horse; go on a wild goose chase; rack one's brains [nerves] without results; scheme without avail; try in vain to ...; waste one's contrivances; waste one's efforts; waste one's labor; scheme in vain; waste one's pains