Jazzie,
Ep's is stressful for everyone. It comes around every 6 months and the initial training is always the hardest. If you had medical problems with shouting perhaps you can get some advice from an ear nose and throat specialist. You dont really have to yell that loud but you can take care of your voice .....
I would suggest that if you want to be a flight attendant you will have tough days and not many ppl quit during ep's so if you get another chance, just suck it up and get on with it...