Finals

I don't understand how people can tell you not to stress about finals when it is the biggest test in the semester. I understand that unless you like really bomb it you won't fail. But lets say you have an A- in a class. You take a crappy final and all of the sudden its a B now. That is money right out of the door. Scholarships look at that. they saw well he doesn't have an A or something and they move on. With college being already being way over priced, how can I, having to pay for every single penny of my college career afford to lose that scholarship? This doesn't make sense to me. I understand the concept of just relaxing and taking it easy. but lets be serious there is a lot on the line, so when people want to tell me to relax and stop stressing I want to tell them well pay for my college and I will. but I don't because that would be mean.