Well, I'd like to start by saying...you are not alone in feeling this way. I am currently a student and feel much anxiety (that's what led me here). So, I hope you at least find some comfort in knowing that these feelings (while they are very uncomfortable and debilitating at times) are not abnormal, and you are not alone.
I assure you...you will NOT lose your mind. "Going crazy" is actually a common fear. The truth is...it is impossible to happen. People can have a lot of anxiety...or even mental issues (these are slow-building processes). Anxiety and panic attacks CANNOT make you "go insane."
You can test this...just try to let yourself go insane. Blab nonsense really loud and jump around (in fact, sometimes it's good to let yourself do that). But realize that the fears you have are unmerited.
Talk yourself down. Say "what's the worst that can happen? If I need to, I can always leave and even go find some help if I want. Everything will be...O...K."
And don''t worry about not having things planned out.
It's ok, life doesn't have to be perfect. It just has to be...lived!
One step at a time.