When you notice your focus in studying has wandered, forgive yourself, and begin again.
I learned this lesson in meditation practice. Sitting in silence paying attention to your breath sounds simple but my mind wanders off. I lose the focus on the breath. My teacher told me that when that happens, I should notice it, laugh that I am human, and begin again. Instead of berating myself for failure, just “ah” and begin again, even if I have to begin again many times.
Be compassionate with yourself. Studying is a skill to practice. Some days our unruly mind will distract us from the work. When we notice, take a breath and begin again.