Get your new set of idioms straight from the horse’s mouth with this article from Tim Bowen.
‘It soon became clear that in supporting that particular candidate, we had backed the wrong horse.’ If you back the wrong horse, you choose the wrong person for a particular purpose, but if you flog a dead horse, you waste time on something you know is not going to happen, as in ‘It’s no use asking him for money. You’re flogging a dead horse there’.
It is rarely a good idea to change horses in midstream (to change your mind about doing something when you are already in the middle of doing it), and if wild horses wouldn’t make you do something, then you would clearly be determined not to do it, as in ‘Wild horses wouldn’t make me eat in that burger joint, even if I was starving’.
If you hear something from the horse’s mouth, you hear it directly from someone who is involved in a particular situation, as in ‘The boss is resigning at the end of the month. I heard it straight from the horse’s mouth’.
If someone gives you something good, such as a present, it is wrong to criticize the present or find fault with it. The response to someone who does this is ‘Don’t look a gift horse in the mouth’.
If you put the cart before the horse, you do something before another thing that you should have done first, as in ‘Hold your horses! (wait a minute) You’re putting the cart before the horse. I think you should check if there are any hotel rooms available before you buy the plane tickets’.