>>11438179try meditation before you study. 15 minutes or so.
Sit on the floor with your back straight, close your eyes. Breathe in to the count of 4, hold to the count of 2 (but do not close your airway, just hold your lungs in the same position), then exhale to the count of 4, then hold to the count of two.
Repeat this until you no longer need to mentally count, and can breathe in that way without thinking about it.
Picture a still pond. No shore, no ducks, nothing but the surface of water. Each thought, impulse, emotion, memory, etc.. picture as a drop of rain falling onto the surface of the water, creating a ripple.
The goal is to acknowledge each "drop" and "ripple" occurred, and then to stop thinking about them. eventually the pool of water will be completely still.
After some practice (5 once a day 15 minute sessions) it becomes easier and quicker.
Clearing your mind for the task at hand can be quite important and useful.
