You said it yourself, you don't want to fail and this is the only chance you have. I don't mean to worry you further but if you begin working, a few hours a day, you can and will achieve but it depends on whether you put the work in.
So, ask yourself, is it worth it?
The answer for is yes, that's why I open my text books and get working.
You've got enough time to do well, be confident and get working - prove to yourself you can do this.