How do you guys study

Like genuinely. I used to be a straight A student, head of the student council, head of my sports team and currently, I can barely pass any subject. Every single time I sit down and open a book, I always end up on some other site browsing the internet like I don't have my final day after tomorrow. This is such a struggle. It's not like comics brought about my downfall, because I used to read them earlier as well, but I feel like I can't balance life with them anymore. To those who are actually good at studying, how do you manage to stay off of the various sites you could be using instead of studying? Genuinely tired of my downfall, please help