First let me say this up front.  I love horses and think that disciplining a horse out of anger is wrong.  Having said that, most of us have lost our cool with them at one time or another and feel terrible about it!  But you can keep a cooler head by simply rethinking a few things.  Limits, authority and long range planning can make for a much nicer life for you and your horse.

Limits

There is alot of pressure put on riders to get their horse to 'like' them.  Parents deal with this too with their kids. We've all seen parents who are afraid to say no to their children and do all that they can to please the child.  Is that a happy child?  No, of course not.  Horses, just like people, need to know their place.  If you look at a herd you know this to be true.  Horses are not democratic.  They don't care about each other's feelings.  They learn who's in charge and they learn to live within that sphere.  Decide on what your limits are and figure out how you are going to enforce them.  Not only will you be happier, your horse will be too.  All creatures like to know what is expected of them.

Be in Charge!

There is only one leader in the herd and if you delegate that responsibility to your horse he will gladly take it off your hands.  And you know, unlike us, who like treat him like a person, he's going to treat us like a horse!  And we've all seen how horses treat their subordinates!  We don't want to be the beta horse! 

True and Tragic illustration:  Years ago, I worked for a farm that had some valuable performance horses.  One horse in particular had been babied because she'd been an orphan and had been hand raised by her owners (bad idea right there).  Naturally they felt sorry for the wee little thing and never set firm expectations with her. But, she was no longer a wee little thing!   I was grooming her one day in her stall and she decided she's had enough and let fly with both hooves narrowly missing my head.  I hollered at her, and the owner came running over and said that I was not to yell at her horses under any circumstances.  Well, I decided that this wasn't the place for me.  I rather like living!  A few years later I heard that the woman's husband had been killed by this same horse.  The mare had done exactly what she'd done to me, except she made contact with him.  He was a lovely man, and certainly didn't deserve that.

Keep the Big Picture in Mind

Think about where this seemingly innocent behavior is going.  It may seem cute right now, when your horse uses you as a scratching post after a ride, but are you always going to appreciate that behavior, particularly when he gets too enthusiastic and knocks you right over?   Or think about the cute little colt that likes to have a sweet little game of tag with you.  Will you like it three years from now when he's fully grown and chases you out of his paddock?  Bad behavior often starts off innocently.  Keep in mind what each new behavior may morph into.  It's much easier to nip a habit in the bud, than break an old one!

Anger can be your friend

Anger is not bad in and of itself.  It's what we do with our anger.  Anger tells us that something is wrong.  That's not bad.  If when you feel angry you haul off and throw a bucket at your horses head, that may not be the best response.  Anger simply lets you know that there is a problem in your relationship with your horse and you need to deal with it.  Sometimes you might need to deal with it right away.  If he's bolting past you and is going to pin you against the stall door, then react right away.  Jerk the chain, give him a slap with your shank, yell at him!  Protect yourself, him and any other innocent creatures he may flatten in his freedom bust.  However, having reacted and gotten the situation under control, it's time to go away and think of what the problem is and come up with a way of dealing with it.  That's our responsibility as the handler.  We make the rules.

Respect Trumps Liking

I'm not advocating that we start to beat on our horses, or hurl obscenities at them.  I'm suggesting that in our attempts to be 'natural' with our horses, we look at how they naturally discipline each other.  They understand that.  More important than having your horse like you, is that you have his respect.  If liking follows, then that's great.  But when working with a creature that outweighs you ten times over, I'll take respect over liking any day.