There is an EXCELLENT article on this very subject in Equss Magazine. I think it's the July issue, possibly June. It might be online too. I'll repost when I figure it out and highly recommend reading the article. It explains in detail the muscles in the neck, the way they work in relation to each other, and how to properly build them up. It also shows the counter-productive things that artificial training aids such as tie downs, draw reins and martingales do.
You just have to see your distance...you don't have to like it.