Pat Parelli has a great saying,"When you take off the halter, and take off the rope, what you have is the truth." That is because most of the time when we ask something from a horse, we give it little chance to say no. If you take off the halter, they tell you the answer they'd like to give, which might very well be no. Now, I'm all for my horses having choice, but some rules are important.
Like this one: Stay In The Pasture, a rule that the horse will never follow, not willingly anyway. I don't care how big your place is, the horse wants more. This is because horses are gluttons. They have no "off" switch. Their appestat is on permanent high.
This VIDEO shows Monty tucking into 20 kg of Competition mix after I failed to close a gate and a door, and maybe (okay, I admit it) the feed bin, itself. So, here is my sister quote to match Pat Parelli's: "When you open the gate, and the feed room door, what you have is about 10 minutes before you have to call the vet."