I work at a resturaunt, and there are times we get quite busy. Always during the rush I feel jittery, more than I think I should because I know exactly how the situation should be handled. I also have an increase in heart rate and I find it hard to talk to people during these times. On one occasion I kind of blacked out and was bussing a table one minute and standing at the back dishwasher the next. Is this normal?