Hydration is key, plenty of water.
Have you considered supplements and vitimans, speak to a chemist perhaps who can point you in the direction of the best supplement to support your lifestyle?
I take multi-vits, cod liver oil and zinc as part of my diet to support busy lifestyle and training.
Breathing is a good point when training which has already been established.
Dont be afraid to load up on a few carbs pre-workout. Carbs are the body's fuel and we need them to have sufficient energy levels and focus. Post-workout, when your body is in recovery it is protein that you need and perhaps a recovery drink or glucose drink.
Good luck