College crisis... kind of

I had something really weird happen the other day. I suddenly couldn't remember why I thought Graduate School was a good idea. I am so terribly stressed out right now, that I don't remember the last time I felt like this. I've never been so close to a nervous breakdown over school!! Sure, I've had pretty rough times in life, but this is just different. Normally the things that really stress me out are emotional or physical (like being sick or twisting my ankle or something like that). I feel like this is totally intellectual stress and that my brain is only capable of processing so much information at a time and unfortunately for me, it's not nearly fast enough. I've never really thought of myself as stupid, but the last couple of weeks have made me seriously question that. I haven't been doing as well in school as I'd hoped; I'm not saying I'm doing bad - I mean I'm passing my classes and stuff, but I'm just not doing as well as I expected and that's been really, REALLY hard on me. Now I don't really know why I'm here putting myself through all this... How do you find hope you feel like you don't even have time to breathe?