Most people have a lot to worry about. Being a student has its own unique challenges and stressors, and there are decisions you have to make which can feel enormous. In this situation, it's hard to not worry about how your life will turn out. Worry and stress can be productive-to a point. Some stress is motivating and helps us perform better. But too much worry and stress can decrease our performance and our ability to make decisions.
Not worrying is hard to do, but there are several techniques that can help you decrease your worry. First, think of worry as a tomato plant. The more you feed and water and pay attention to your tomato plant, the more tomatoes will grow. If you leave your tomato plant alone, it will die. Worry is similar to that - the more attention you pay to your worries, thee more they will grow.
One thing you can do to decrease the time you spend on your worries is imagine building a box in your mind that will hold your worries.. Be as detailed as you can, and be sure to put a lid and a lock on the box. That box will keep your worries safe for you until you have time to think about them, but it will keep you safe from thinking about them at inopportune times.
The second technique you can use to decrease your worries is to set aside a specific amount of time to worry. Saying "I'm going to worry from 3-3:30 pm this afternoon about my test" is better than worrying about it all day. This will help you decrease the amount of time you spend on worry and will free up your mind to think about other things.