This SUCKS

I just took an organic chemistry exam. The scary part was, it was easy. Our professor as a gesture of kindness decided to let us have an open book/notes exam, which is weird to begin with for this professor but she also said she wasn't going to make it any harder than a normal test. Terrified, i went to the study session last night, stayed all the way to the end and wrote down everything we went over and then it was ALL on the test. So basically i had the answers to all the questions. Why am I still scared?