This advice, and a dollar, will get you a cup of coffee....
When you get to Basic, I suggest two things:
1- work as hard as you can, as long as you must, and
2- sleep 8 hours a night.
You will find that you can work an awful lot longer, and harder, than you ever thought you could. Realise this, and never give up. I feel pretty confident that I am not alone in stating that I will put a LOT more effort into helping a trainee that is truly giving his or her all than I would give a slack individual.
Re sleep: I have been on a course or two, and early on realised that if I didn‘t get a minimum of 8 hours sleep a night, I simply didn‘t absorb all the information that I was expected to learn the next day. Note that there will be times when you will go several days without sleep, and weeks with a couple of hours sleep out of every 24. These times are called "the field", and are not basic training.
Many folk get behind on the non-essential stuff. For instance, your boots will NOT be "good enough" until at least half way through the course- do the best you can, but don‘t stay up all night working on your boots, not any other item of kit. Learn what you have to learn, do your best on your kit, then be properly contrite when your NCO blasts your boots- he‘s paid to do it, you‘re paid to listen. It‘s part of the training.
There have been a lot of folk go through basic, and they were all worried too...most made it.
Again, work as hard as you can, and sleep.
Lastly, if you ain‘t having fun, take a long look at how you‘re living.