School struggle and no more discipline/ What to do?

Hi. I'll be 16 next month and have my first two final exams for secondary school in about a week. One in German and one in English. My grades have improved incredibly compared to 5th and 10th grade. My half-yearly report was a 2.0 in all my main subjects. I have a dream and that is to be accepted into my dream school and to complete my Abitur there. I already have a provisional acceptance. My final report, however, is the actual enrollment. (The school has very strict requirements for main subject grades.) I know myself well enough to know that I often push the boundaries of learning. That means going out is a no-go and studying is a must. I've been studying in an unhealthy way. A few weeks ago I was at a point where I wasn't feeling well physically and mentally and although that made me feel bad, I was mostly worried about the time I was losing for studying. I hope it's easier to understand when I say that I've been studying in an unhealthy way. My grades have become more important to me than some (justifiably) unhealthy comfort zones like TikTok, Instagram, Snapchat, or YouTube. I no longer own those apps. I've never been a fan of video games, and I've set my phone to only have the essential functions (making phone calls, texting, etc.). Now I've reached the most important point in my secondary school life, and although I studied over the weekend, I know that I spent far more time reading my leisure books than memorizing my school work, and I'm simply disappointed in myself. These phases of not feeling like studying are fine, but I'm afraid that I'll make too many exceptions and lose control. I've removed the necessary things from my life that distract me. What I haven't mastered yet is that discipline. I ask myself, "Why aren't you doing what you're really meant to be doing right now? It's actually something you can enjoy and be grateful to be allowed to do. Learning." God, and then I wonder if I'm being too hard on myself again and should let my hormones run wild at my age, blah blah blah. I want healthy discipline. I know it'll take a while to get the hang of it. But I simply don't have the time anymore. I want to trust myself when I set myself a goal. It's funny, if I were to break someone else's promise, I'd be deeply disappointed in myself, or I wouldn't even let it happen, but when it comes to my own promises, I blame everything on my teenage life, puberty, and my hormones. I already have a weekly schedule. There, I've assigned myself study boxes for the day, which I often have to exceed because it takes me longer to cover the material. Oh, somehow, if something bothers me, like my former TikTok addiction, I've deleted that app. I've often tried to teach myself the discipline to say "no" to an app so I wouldn't have to delete it, but it obviously didn't work. The same goes for other apps. I can't just delete everything from my life just because I lack discipline. My phone time still amounts to over four hours, and it makes me incredibly sad. In those moments, I wonder if it wouldn't be better to go back to studying unhealthily, since that's how I got good grades. I literally couldn't think about anything but my schoolwork. How do I best strike a balance between healthy and unhealthy time, and between free time and study time?

Would be nice to hear answers here 🙂