Day Star has protected me before. She did it when I fell and hit my head. And when I was putting hay in the rack. Day Star chased everyone away, even her best friend! She surprised me the first time but after that I understood what she was trying to do and say by those actions.
That's what I thought at first thought when I put it in the rack she walked away from the horses and let them eat it. She was waiting till I took out the next loaf to eat from. The other horses where so hungry that they where pushing me around and I almost fell but Day Star came to help me.
It is actually not always something to be happy about. A horse may protect another member of the heard if he feels obliged to help somebody that is weaker, thus, lower in the pecking order of the herd, for example, a foal or a youngster. Alternatively, a stud/gelding may protect a mare in a battle for hierarchy. That means that the horse who is protecting the herd member in question - and that can be a human - is seeing himself as a leader (thus responsible for the well-being of the weaker member) over the one who is being protected. In such cases, the relationships with this horse will go fine and dandy until the human asks something that the horse thinks is disrespectful to ask...
A good thing to remember is to try not to humanize horses too much and not to expect human sense of justice from them.
Well, I'm really glad there's at least one person in the world who can surely know what horses actually mean and feel.
Sadly (or gladly) life ain't no Disney. Misinterpreting actions of a horse can badly hurt anyone one day, so does antrophomizing (humanizing) a horse. It's just too much responsibility on a being that doesn't reason by our rules. And this I say as a firm believer in that a horse can have a deeper affection and understanding towards a human (as tacky as it may sound, my gelding has actually chased an attacking stallion away from me in order to "protect" - and he also tends to try dominating moves over me as often as he can). It is just that they still are horses at the end of the day, and rather than applying human sense of justice, love and friendship on them, we should stay attentive, focus on what their natural behavior teaches us and keep learning about their "language" and principles of life. That makes a happy horse and a happy human, and keeps us all away from nasty accidents.
I only had one horse over the years the protected me. It seemed as though she was protecting me anyway. Once, she got very excited and flew up in the air out of the blue, I wasn't paying attention and fell. She came to an abrupt halt and stood over me. When others tried to come near, she pinned ears and charged them, returning to me. It was strange but... It seemed like an attempt to protect me. That or she wanted an opportunity to buck me off again. Ha ha