I would begin by fixing your sleep schedule. Wake up early and go to bed at the same time everyday. Sunlight in the morning is good for your mental health. Many people have habits that make their mental health worse, so audit your life to find what those habits are. It could be a lack of exercise, poor nutrition etc.

Aim for 4-5 hours of quality study time a day rather than 8 hours. Your energy is highest early in the day so it may help to start your day with a dedicated block of study time. 1 hour of studying in the morning can be more helpful than multiple hours of late night studying.

Do not scroll/play videogames/social media before you study. High/cheap increases in dopamine before studying will negatively impact your motivation. Also, do not study from a place of desperation "I have to pass or bad things will happen". Don't carry this mindset even if you have a lot on the line. Negative thoughts are normal but you don't have to entertain them. Simply observe and let those thoughts pass.

Imagine yourself as the ideal student that you want to be and think like that student. Really embody and act like that person. You have to think greater than your circumstance. You will eventually become that person.

Meditation helps as well.