With all the foundation training people do with their dogs in order to train the necessary skills, what would help the most would be to put more effort into building a stronger relationship between the dogs and their owners. That relationship is the key to getting great performances and just having a better companion. How do you get a better relationship? It's simple, become a better leader to your dog.
Dogs are not comfortable in enviroments without a leader and without structure. And depending on the personality of the dog, they will learn various ways of dealing and coping with any uncomfortable situation.
Many humans will bring new dog or puppy into their lives and try to treat their relationship like a new best friend. My dogs most definitely are my best friends, but they only became my best friends because they respect my leadership and the structure that I provide them. I'm not talking about total dominance, I'm talking about balanced dog training - where we (the humans) are training the dogs rather than the dogs learning how to train the humans. Dogs think about life and living much differently than we do. They deal best with straighforward situations which are black and white. They do not do well with our human negative emotions and they do not understand our verbal world of communication, but they are masters at figuring out our physical communications (motion) and signals.
My dogs never cease to amaze me at their ability to watch me and figure me out. I remember one time where I went to turn on the lamp in the family room, only to find all 3 of my dogs slinking away to various parts of the house (I saw Reason's tail going around the corner, Gimmick went behind the couch, and Score went slinking off into the kitchen). "What in the world was THAT all about?", I thought to myself. It didn't take me long to figure out what they were responding to - that lamp never gets turned on unless the dogs were getting groomed. It just happened to be a stormy/dark day and more light was needed in that room. The brilliant interpreters that they are, my dogs had figured out the pattern. If you pay attention to observing your dogs and their reactions, it can make you a much better dog trainer.
Occasionally I will hear someone express that they have someone else bring their dog to the vet (or be involved in any situation that they view as negative) because they don't want to be associated as the bad guy. This setting up a poor relationship pattern with your dog and it is not being fair to your dog as they look to you as a leader. Dogs are going to have to deal with fun things and not-so fun things in life. That's the nature of life and dogs and the choices they learn to make. They deal with negative things by avoiding them - and that's to be expected. But if you are not there to help support them unemotionally through some of these required "not-so-fun" experiences, how will you be there to support them when they decide that they don't want to do something that is required or when they decide they want to do something that is not allowed in their day to day lives? That will lead to training issues down the road in your favorite dog sport.
When you train specific skills to your dog in agility, obedience, or herding, how will you help them understand the parameters of the skill you are trying to teach, if you are only exposing them to positive things? How will they deal with the negative things or even the difficult or challenging things in life and in training, if you are intervening and not allowing them to make a choice? You might create a very dependent dog that simply can not deal with making mistakes or failing in any situation. These types of dogs will shutdown or slow down and stop trying as they stress out because they can't depend on you to help them. Or you might create an entrepreneur dog that gets creative in dealing with things that they don't want to deal with or challenges their focus and skills. These types of dogs can learn how to seek out and find their own reinforcers or fun things to do when they are not taught that the choices they make leads to outcomes that are even less enjoyable. Neither of these situations is going to give you a great relationship with your dog and it will certainly create future training issues as the dog learns effectively how to avoid or resist those perceived "unfun" or uncomfortable challenges in the future.
Dogs deal better with negative situations by having a strong unemotional support system in a strong and dependable leader.
Yes, training new skills should be done with positive associations and experiences. But dogs should also be allowed to make mistakes along the way and eventually learn how to deal with those failures based on the outcome of their choices. Dogs that are never allowed to fail or make errors or experience negative situations, are much more of a challenge to train for any dog sport. Proofing games are an important part of training dogs to really understand the skills they have learned so they can perform in any environment and have a clear understanding of their job. However, you can't effectively or fairly proof a dog that doesn't deal well with failure or mistakes. And as a trainer, you must be able to allow the dog to work through mistakes without jumping in so quickly to try and help them. Dogs that learn to keep trying when they've made a mistake are dogs that have great relationships with their owners. There is a strong connection in place as the dog looks to the owner as a leader.
So set aside some time and observe your relationship with your dog. Are you too quick to try and intervene to make each experience a positive one? Do you let your dog make mistakes and unemotionally give them the response that is needed to help them make better future decisions? If you are having issues in obedience, agility, or herding with your dogs, take a few moments and be honest with yourself about some of the relationship and leadership issues that occur around your house. Sometimes honesty is the best medicine on the road to recovery.