You are not alone in experiencing this and perhaps the following explanation can help you understand the underlying reasons for your actions so that you can re-direct your efforts towards your top priorities.
As students, we often do not know what is expected of us by our instructors, including at this juncture in the semester, what upcoming tests will be like and what assessment criteria will be used, and how we will be graded.
This lack of clarity and uncertainty can lead to anxiousness or worry about the exam and our performance on it. These emotional responses can disrupt our attention and make it hard to concentrate in a way that is necessary to actually engage deeply in the studying and exam prep we need to meet Princeton course standards.
Those uncomfortable, aversive feelings associated with the exam can also repel us away from studying. This understandable impulse can lead us to escape FROM studying and INTO activities that reduce our feelings of stress, albeit temporarily. These activities– like binging videos or mindless scrolling–often reduce disrupting feelings in the moment, but with the result of increasing later stress. When we resume studying we have less time so may feel greater pressure and frequently feel guilty about our avoidant actions. So, our actions did not improve our emotional state for studying in the end.
What can you do about this cycle if you find yourself in it? First, address your assumptions. Recognize that some uncertainty about exams is to be expected, and some is inevitable. Experiencing uncertainty is not a sign of a problem IN you, even though it causes you stress. Some uncertainty can also be alleviated. Take steps to gain a clearer understanding of the format of the exam, its scope, instructional materials that will be emphasized (e.g. lecture more than textbook) and most importantly, gain an understanding of the types of questions/problems you will encounter and the kinds of thinking and study they require. This will provide you a target to aim your studies at and specific tasks to practice in preparation for performing on the exam.
There are many possible sources of information on these aspects of the exam. Review the syllabus and other materials. Ask your professor and TA. Analyze (not just take) past course exams. Talk with other students, read course reviews, and see if there is a relevant Principedia article. Studying in a purposeful, targeted way can increase your confidence and practicing under exam-like conditions can reduce test anxiety experienced on the exam. McGraw has resources on exam prep, and you can read here how academic life and learning consultants dealt with their own challenges, including test anxiety.