When training remember to breath naturally and relax. It seems like such a small thing to do but it will really help you to become a better martial practitioner. In your training breathing naturally and relaxing will allow you to receive the information your teacher is presenting as well as keep you from getting tired. I cannot tell you how many times I have watched someone during their training and noticed that they are tensing up and not breathing naturally. During the course of your training do not make this mistake. So what is breathing naturally? Simply put, just breathing when you need to! Let your body do the work for you and breath naturally without holding your breath unnecessarily. If you breath naturally and let your body take care of it you will also be relaxed. This will all help in the learning process!
So breath in, breath out and just let it happen!