Have you learned to read your dog's frustration level?
It's important to pay attention to your dog's reactions while doing any type of exercise. If he/she starts barking at you especially, it's time to change the exercise and make it a fun game. The repetitive quick barking is a high sign of frustration. We want to keep the exercises a game. Even playing tug of war can be made a fun obedience lesson. While playing tug, give a sharp command to let go (Drop or Loose) and as soon as they let go-give it right back for the reward.
But back to my point: another sign of frustration during obedience practice is when your dog is constantly not paying attention such as playing with every leaf nearby while in a down position, for example. Keep your dog focused on you by making every exercise interesting. I know obedience can be tedious. This is very true when we're hell bent on trying to get that one last thing right. Remember, short and often sessions- 5, 10 minutes, but no longer than 15 mins on a good day!
Do different combinations of Stay, Come, etc. maybe try downing your dog halfway to you. Be creative. We're the thinking species here. Your dog just wants to have fun but when we think about it we can teach or reinforce behaviors by making them work for it if the reward is worth it. Reward with praise always; mix in play and high valued treats and your dog will be jumping for joy! ALWAYS finish on a high note. This means with something the dog did well. If the frustration is too high and you decide to end it, just down or sit him/her and praise. Happy Holidays.