Frustration: The feeling of being upset or annoyed, esp. because of inability to change or achieve something. The prevention of the progress, success, or fulfillment of something.
No one likes the feeling of frustration; it can literally make you feel like pulling out your hair. Dogs don't like to become frustrated either; it can lead to fall out behavior or a complete shut down.
As a dog trainer frustration is something that you must be aware of; for the untrained or inexperienced it may go unnoticed. Frustration comes in many forms and when it is a dog who is becoming frustrated it may present itself in a hidden form.
Frustration is typical in training; sometimes it is hard for our dogs to "get it." If the training goes on too long without some sort of progress a dog may become frustrated. If what you are doing is not working; you much switch gears or move on. A very good example is when you are teaching a new puppy, and you are using a food to reward behavior. Most puppies just want the treat; if they have to wait too long for the treat they will start to exhibit some unwanted behaviors like jumping, whining or biting. So what do you do if your dog becomes frustrated?
The solution to this problem is to break a behavior down into baby steps. For some dogs the whole picture may be too much to undertake; so breaking it up into understandable steps will allow for success and progress. Say you were trying to teach a "down" and your dog was just not getting it leaving you both frustrated. Although the goal may be to have your dog do a lay down, you start rewarding them for lowering their head, then their neck and head, then for putting one foot out, then slightly lowering their body until they are in a down position. Once you get to the final goal your dog will more than likely have an "ah ha moment."
Again patience plays a huge factor in the learning curve. If you lose your cool; stop and walk away. Never train in an angry state; it is just not good for either of you. Learning should be fun so when it stops being fun, stop. When you see that your dog is not understanding what you are asking; ask for less and reward both of your success.