How can I rebuild my confidence?

Several weeks ago, I began my new temp job at a law office. The first day, I felt excited to be starting something new. Then a couple of hours into it, I started to not feel so good. I was overwhelmed by everything; new people, new environment, company procedures and acronyms, etc. I kept trying to tell myself that this was just a temporary gig, but I couldn't shake off my feelings. I felt as though I had to learn a plethora of information in a very short time in order to complete my job. Everyday, I would come home feeling very tired without much of an appetite, and wanted to be alone, lay down in bed, and sleep the rest of the night. I felt like a rat in a cage, being stuck at my cubicle all day; quiet, a little dark, working on assignments I felt like I couldn't grasp without asking someone for assistance over and over and over again. This has really taken a toll on my confidence. I feel like I'm mentally crippling myself. How can I rebuild my confidence? I feel so sad :(

Well, it sounds like you got in over your head AND you're a perfectionist. You went to work in an environment that was completely uncharted waters for you. You obviously don't have any experience in the legal field. The temp agency, nor the employer should expect anything more out of you than menial tasks such as answering the phone, filing, typing, etc... and you certainly shouldn't expect yourself to be able to do things you're not trained to do.
I was in the same situation with an investing firm; temp, didn't know squat...they had me calling investors to get numbers, etc... It was awful! It ended up with me crying and going home after about a week and a half. I was about 20.
At this age, 40, I would speak up instead of beating myself up for not being able to do something I'm not trained for.

It's not the job. It's you. You should find an outlet like exercising or find a hobby. I'm not trying to be mean, but if you really think about it, it's true. Please don't take this the wrong way. I had a similar situation happen to me. I got a promotion and I was so happy but then I decided that I didn't like the job. I stuck with it. Now, things seem to be getting better. Make sure you eat right, get plenty of sleep, exercise and get involved in a hobby.