It doesn't seem fair sometimes and it doesn't seem to matter a healthy lifestyle or a haphazard one, one in eight women still cop breast cancer. Beats the heck out of me what the cause is but your focus needs to be on getting through the treatment. Yes, GET THROUGH IT. Time enough to worry about what you will be like and what sort of life you will want to lead once the hard stuff is behind you. Its tough on partners too so try and be sympathetic and encouraging on your good days. Get as much rest as you can, it will help. <3