Its really tough to deal with such situation especially with your parents. When you have to maintain your respect to them whatever happens and no matter how disappointed you are.

One thing I can tell you is that be calm when you explain things to them. If there are things that you don't want to tell them, just tell it to them. They ought to respect your decision. Sometimes parents just can't accept the fact that we're no longer a child and they are used to treat us like one.