It is quite common to get frustrated in the process of learning. First and foremost, it is important to develop a keen interest in it. Then, it shall be of utmost important to you and give you more interest and fill up you mind with complete knowledge along with wisdom.
Most of the children might face some difficulties in their studies simply because they might be termed as lazy; but in fact, few of them face the problem of learning difficulties as they might be slow learners and show the symptoms of learning disability which is gravely responsible for hampering the career of the child.
But, if the child does not have a learning disability, he should make it a point to work harder and show interest in studying along with more physical activities, so that he can be smarter and more active in his life. The mind can also become sharper while doing meditation and seeking help from God Almighty through the actions of spirituality. It is also a must to have a balanced diet and keep yourself away from hunger and drink enough water daily in your life.
Keep yourself away from stress and concentrate only on the positive side of life. Take a short break while studying and believe in yourself that you can do everything and try to become smarter every day by reading books that give knowledge and help you avoid being dull and lethargic.