Belinda, so sorry you've had a crap day.
You know even us working florists get it wrong sometimes too- sometimes a bouquet just wont go together and look right whatever you do to it (I've chucked many a bouquet against a wall in anger when its not worked- a TOTAL waste of money but made me feel better!). You do need to get used to working under pressure (thats like any normal shop enviroment) and these exams are good practice for you.
It doesn't feel like it at the moment but you ARE learning from this and it will make you a better florist from it, we've all had to go through the same. Please have faith in yourself, the work you've posted in the gallery is proof you're coming on really well- you're going to make a really great florist!
Jo x