Remember to be aware of (but again without concentrating on) the rhythm of your opponent's breathing, this will reveal his physical and psychological condition and it also can be an indication of when you should attack. When his lungs are empty and he's just starting to take an in-breath his reactions will be slower and his muscles less responsive.

Control your own breathing - keep the in-breath and out-breath equal in emphasis and smooth - and you will not only give your opponent a discouraging impression of imperturbable confidence, but will actually increase your confidence.