One of the best ways to avoid frustration is to always try to end your practice with a success (when applicable). It sends an entirely different message to your subconscious then ending with a neutral result or a failure. The last two situations leave you with the expectation that the next test will be just as messed up, and you focus on the negatives. However if you end with a success you end up expecting to do the same or better in your next practice. This is also easy to do, either don’t stop until you get a good result (provided that you still feel able to go on – generally spending too much time trying to do something can cause strain) or stop when whatever you were trying to do works. So thus with a little maneuvering you limit frustration and potentially boost your rate of success in the next practice instead of lowering it.
Note: This is more for if you can stably get good results given a short amount of time. If you’re just starting out or are having trouble with the skill, keeping a practice up for an hour until you finally get something to work is probably not a good idea, or healthy. Use a bit of reason. “Don’t stop” means maybe you extend things five or ten minutes, not an hour. There are some practices you might just have to call off, since practicing for an hour is kind of frustrating too.
Practice like usual, and when you experience a small success, end practice for a little while. Do this for a few days and see if these added confidence boosters result in an improvement.
You should work on this concept for at least 6 days before proceeding.