Sometimes it takes a lot out of you when you study a new language. At the moment, I am doing an intensive course at a private language school. I have had an opportunity to meet new people from all over the world and see firsthand how difficult it gets sometimes to stay focused and be motivated.
We are adults. We have more than enough on our plate without having new German words to learn every day. We have families to take care of, some of us have children, others have to constantly look for a job. We want to achieve higher language level fast. We find time to do the homework in between housework/taking care of children/studying other subjects/worrying about the future, etc.
Very often, there is no one around to give us enough support, to help us with the difficult grammar topics, to correct our mistakes. Language school is like a home for us now. The teachers do not laugh at our mistakes and help us all the time. We feel comfortable at the school, but we are vulnerable when it comes to the outside world. We do not feel confident about our language skills when some strangers do not understand our pronunciation or cashiers scream at us when we can not insert a credit card into a payment terminal fast (despite the fact that a cashier explained to us what to do in German).
It is easy to lose the motivation for speaking the language when you feel that teachers misjudge you. A friend of mine got surprisingly bad grade in speaking, even though he had worked hard. Grades are important for us, they are the confirmation of how well we do. Good grades make us happy at this difficult period of our lives.
The point is, we shall not act silly. We shall stay focused and remember that what we do now will help our future. Bad grades do not indicate we are stupid, they remind us to work harder. Sometimes, small things can make a difference. Maybe another hour of sleep will help your brain to work better. Another 10 minutes of learning will help you to improve your reading/speaking/listening skills. An additional question will help you to understand the learning materials better. Learning is not necessarily easy all the time. Sometimes we shall remind ourselves we have all the abilities to achieve our goals. It does not matter what other people say as long as we are sure about our skills. For example, if a native speaker tells you that his/her language is too hard to learn, do not be scared or disappointed. As long as you follow your plan to achieve the aim and do not let others to distract/discourage you, you will be fine.