I recommend the Pomodoro technique during studying or writing papers - 25 minutes working followed by 5 minutes of rest. Do that 3x. During those 5 minutes, step outside or sit by a window, enjoy the sun on your skin, and look out into the distance. Avoid doing anything that stimulates your mind (i.e. reading, looking at your phone, etc.) because the point is to rest your mind. After your 4th round of 25 minutes working, take a 30-minute break. I recommend 25 minutes of something fun - a show, a book, a game, etc. - and then the last 5 minutes resting your brain before jumping back in.
While working, enjoy a yummy treat! Something you can snack on or sip to bring some pleasure while you study/write. Maybe music if that's not distracting (wordless music is probably better, but everyone's different).
You could also change up where you study to spice it up (library, friend's place, cafe, etc.).
When you finish an exam, celebrate! Do a solo date or celebrate with friends. It can be as big or small as you want. You deserve it!