Dear Peter,   
Don't worry about your study too much. First, you should learn how to relax yourself. Doing more sports is good for your health. Listening to music is also a good way to relax yourself. It's necessary to have healthy eating habits, too. Remember to have breakfast every morning. It can give you enough energy to study for the whole morning. What’s more, you'd better go to bed early and have enough sleep. It will keep you active during the day. Finally, you should talk with your friends, parents or teachers often. Tell them about your thoughts and feelings. Try to get help from them.
    I hope you can be happy and study better.