There is no such thing. 
As you become a better rider, you begin to run into obstacles that were previously unnoticeable. Invariably, there comes a time when the simple becomes complicated. Without warning, riding becomes more than just the various gaits and transitions, more than a turn with the hands. You read and study and watch and discover that there is so much more to each gait, more to each turn, and more to the joys of riding.
The original walk that once felt adequate is no longer satisfying. That wonderful canter is now not quite balanced enough. You discover nerve endings where there were none before, and you are inspired to reach for new heights thanks to energizing "feels" emanating from an enthusiastic horse, confirming more than ever that you are on the right path.
The joy that went along with the simplicity of riding might be temporarily gone. You approach days of confusion, questions, and ultimately, frustration. You wonder why there seems to be so many details, so many little nuances that change sometimes on an even daily basis. And you begin to wonder:
Why is riding so difficult?
The quick and easy answer is that riding horses is about combining many and varied details into one - nothing can be achieved in isolation.
Everything matters:
- the mood of the horse
- the weather
- the horses around you
- the regularity of the the exercise the horse gets
- the type of feed
- the riding environment
But there is more!
Aside from the environmental factors, riding is an especially difficult sport because of the balancing requirements inherent to moving through space on a living, breathing animal. Charles de Kunffy says it so well in his book, The Athletic Development of the Dressage Horse (1992):
The partnership between horse and rider is difficult to achieve and even more ambitious to make beneficial to both. Horse and rider posses the two most unlikely anatomies to be harmoniously united for the purpose of progressing effortlessly through space. The horse has a narrow, precariously balanced, horizontal structure, much like a pipeline. This structure has narrowly set, weak underpinning, the legs, bridged by a weak back. There, almost at its weakest point, the most unlikely candidate for partnership, the vertically pipelike human, wishes to intercept at a 90-degree angle. Both are creatures of precarious balance, even when left alone to cope with the ground. In riding, we wish to harmonize our balance with the horse's for common progress through space. (p.2)
Obviously, there have been thousands upon thousands of "mutually beneficial" partnerships in the past and in the present; apparently, the human body can in fact become united with that of the 4-legged horse that travels so relatively effortlessly over the ground. The trick is to learn how to become harmonious - how much to give, how much to take, and when to accept what is being offered to you.
So many questions!
You must learn to differentiate between too much, too little and just enough; between too early, too late and just in time; between resisting, energizing and being plainly passive. When is the horse going too quickly, too slowly, too enthusiastically, too lazily? What do you do in each case? How do you combine all your aids to communicate the right message at the right time? How do you not only refrain from interfering with your horse, but even learn to improve your horse to become better than his original state?
What is the answer?
There is no easy answer. The most obvious consideration is to seek out a credible instructor well versed in not only in all things 'horse', but also in instructional techniques and experience. There is no replacement for an 'eye on the ground' - no blog post, no (however well written) book, and no video - although such media do play a role in the over-all education of a rider. The person on the ground is the one who translates what the rider is doing now into what the rider can do in the future.
The other task, however difficult, is to try, try, try and try again. Pack it in one day, and start all over again tomorrow. Learning to change muscle memory and developing a blueprint takes time, dedication and repetition. Each time you change the 'rules' on your horse, be ready for a step backward before a new step can be reached. There is no other way.
Be patient - with yourself and your horse, and find joy in the pure accomplishment of learning from your horse; focus more on the journey rather than the goal. As Mr. de Kunffy writes so eloquently, "Riding is, therefore, an ongoing, never-ending, challenging process. That aspect makes riding so intelligent and significant an effort. One merely strives, one never arrives." (Ibid, p. 4)
