You're right - you can't do anything about your results now. But, they do not define your life. Maybe you'll need to take a different path in life to get to where you need to be, but everything happens for a reason. Remember that you did the best that you could and that's all that anyone could ask. "Grow up" isn't a good phrase for them to use at all - your emotions are very real to you and you need to deal with them rather than just try to get past them as "Grow up" implies.
When you're upset or stressed, try to write down or tell a friend why you feel that way. Explaining in detail about what's making you feel that way can help you come to terms with it mentally.
Maybe try telling your parents about how they make you feel? Sounds like they really are not helping your emotions.
**EDIT: in high school, i was convinced that I did an awful job of my exams. turns out, they were excellent and got me into one of the highest performance colleges in the country. IMO some peoples minds look for every negative thing that could influence your results, and only focus on those, therefore making you believe that the results aren't good. You don't know what your results are until results day, so try not to worry too much.