1st to know what you should be breathing with:
take a kitchen chair, sit on it comfortably, feet on the ground, knees together above your feet, lean forward - chest to your knees, have someone sit on your back, the heavier the better – RELAX, exhale
- you won't be able to breath with your chest
- you won't be able to breath with your stomach
+ you’ll get the feeling to breath with your waist

Practice this breathing in all situations – use your waist - will lower your point of gravity to your abdominal region - will make you calm and stable.

Stretch your spine – bottom goes down, hip turns back, chest up, chin back, crown up, shoulder down; no joint is ever extended to max, always keep a minimal curve.

Keep constant tension in your abdomen - increase it when breathing in, relax a bit when breathing out.

Be safe (keep proper distance) when breathing in, especially at maximum inhalation; act when breathing out. Keep breaths to minimum and at high frequency.

All must be comfortable, not overdone, not forced - first meditate, then do simple movements, then katas (for months, years, not just minutes!!!) - concentrate on breathing, find your rhythm, don’t suffocate, don’t wheeze, enjoy

Practicing zazen, kyudo, taichi and aikido helps with these.

Be patient, move when you must, dodge minimally, act once, but then act for good - it is all about timing.

When you'll get to perfection with this point you'll forget that you've ever wanted to fight at all - there's no need for it.

Keep practicing, allow yourself to fail, just keep starting over again.