don't want to quit my job

I just took a new job with a utility company in Michigan. After having been unemployed for 15 months, I was excited to finally find some type of work. Long story short, the job requires intensive training and part of that training involved getting up in front of the training class and demonstrating what you've learned. Once the trainer informed the class that TODAY was the day, I lost it. Sweaty palms, head spinning, stomach tossing, extreme shortness of breath. My mind suddenly erased itself and this all happened while my other classmates were each taking turns demonstrating...my turn had not even come about!!! I became so overwhelmed that I quickly grabbed my briefcase and scurried out the door in tears. Luckily no one saw my shame. My partner in class alerted one of the trainers who ran after me. Too embarassed and ashamed to return to the class, I refused numerous offers to rejoin the group. I was told to go home tonight and think it over before just quitting and to call my manager on her cell phone. As of the time of this writing, I can't find the courage to call the manager and give her an answer either way. Feeling horrible, embarassed, ashamed and disappointed in myself.