Is it okay if I panic now?

Tomorrow 1:00 I have my last final. I haven't really started studying yet. I have an A in all the other work so even if I only get 70 points in this 30% I'll still have an A. If I don't go, I'll still pass. I already got my other course grade and it was an A.

So, what's with the terror? I have only been going to college since 1968, you'd think in almost 40 years I'd have had a "few" tests and be use to this? For my first degree 68-72, I didn't do the work, didn't read a thing, went through college on what I learned in high school and my "native" intelligence and got C's so what's my fear now?