Eyes on the Future, Heart in My Throat

I just e-mailed the three professors I would like letters of recommendations from. I have no idea what I'm going to do if one of them says no. There's only one I'm worried about. I'm praying she'll be merciful because her recommendation would be invaluable and I have no back-up.

Yikes.

Also, why are the GRE subject tests only offered three times a year? I don't get their system. And I don't like how it makes me panic.