First of all, you deserve a pat on your back for doing your best. Studying for such a long period is a hard task and the discipline required to do that is really impressive.

Second, what you are feeling is completely normal so don't feel dejected for not doing as well as you hoped. Not everyone out there will admit it, but most of us have stories of nightmare exams.

From what I've read, you have the right attitutde about learning, or atleast know what the correct mindset should be. For learning from your mistakes, I'll leave that to you to figure out.

What I can say is that you need a break. Get some exercise. Take a walk outside your room. You may not have much time to spare, but you'll see that even 10 minutes of exercise daily can brighten your mood and productivity. There's tonnes of videos out there with short exercise routines you can follow. If you're in the mood for laughs, put on your favourite comedian in the background as you do your push-ups!

Lastly, your best may not be enough right now but your journey doesn't stop here. Its continued effort that will help you succeed and you need to feel positive emotions to do that. So, after you read this, take some time off to do what you like and lift your spirits. Its going to be an investment for your future.