Never eat less than two hours before practice no matter what shape you're in, you WILL throw up.
This, and even if you don't you will have less energy for your training, because it will pull a lot of blood out of the rest of your body (including your brain and your muscles) and redirect it to your digestive system.
And concerning the conditioning, learn were your limits are. It's ok to cross the limit from time to time to get to know were it is, but it's of no use to regularly go over it. When you know that you are close to the limit, just slow down. When you slow down, at least you will be able to continue to train, whereas when you go over the limit you will have to stop training for that session.