You need to take a deep breath and break it down into smaller steps. What can you accomplish in the next week? How often can you study, how can you balance it with time spent with friends/family etc. Give yourself a short term goal. For example, “I want to do x amount of revision a day, for this long and at this time”
By giving yourself a roughly scheduled revision time, you are making sure you get it done and still have time for other things. Whatever it is you need to get done, try to break it down. Trying to tackle it all will only knock you back when you realise you can’t handle it.
You are not “dumb” for coming up with an idea like that, it shows you are motivated to a degree, and you’ve got to build on that momentum. Finding an ultimate goal has helped me to think positive and stay motivated.
Think of it this way. You could try incentivising yourself, working towards something small which you enjoy. If you decided to go this direction, it should end up in you feeling like you’re rewarding yourself, and it should feel good.
I’ll leave you with this: Remember to never sacrifice your happiness for an A. If you want that A, keeping yourself happy and focused will drive you to achieving it.