As a Recruiter, I have seen several people leave for BCT and be successful. I have also seen some come back. Here are my tips:
Do your best to keep your motivation high at all times.
It's going to be hard. It is supposed to be challenging. Just keep in mind why you enlisted and remember that you will get through the hard times by staying motivated.
It isn't personal.
The Drill Sergeants are Professionals. They are selected based upon their ability to turn citizens into Soldiers. That is the mission of a Drill Sergeant. So if you get fussed at by a Drill Sergeant, it is only to train you to be a Soldier.
Don't worry, you will. Friends who are going through this with you will make it easier to get through the stress. Friends will also be able to help you with the things you are weak on, as you will then with the areas they need help in.
There is a reason for everything you do.
Keep in mind you may not know the reason at the time, but there is a reason, so do what you are asked and stay motivated.
You will be doing something different from any experience you have ever had in your life. Look for the fun parts.