to hear straight from the horse’s mouth = to receive information from someone who knows the facts
I either heard them from friends or straight from the horse’s mouth, which in this case was my father.
If wishes were horses… = is used to say that it is useless to wish and that better results will be achieved through action
— If only I got this job!
— If wishes were horses…
Hold your horses! = to hold on, to wait; to stop and consider carefully their decision or opinion about something
Irritably — she really wanted that cup of tea; she was growing as bad as the British — McAllister turned off the gas ring, blew out the match, and walked to the front door, grumbling to herself, Hold your horses, I’m coming, I’m coming, when another urgent series of knocks sounded.
to flog/beat a dead horse = to waste time trying to do something that will not succeed
Do you think we will pull the project off or am I just flogging a dead horse?
to eat like a horse = to eat a lot
She eats like a horse and never gains an ounce.