@pinkhope
It's not unusual to feel up and down given the diagnosis.
Please don't be hard on yourself!
Petrea King is a presenter on ABC Nightlife - worth checking out the book mentioned and/or her podcasts.
Hopefully you will find the coping tools. I found early days that down was there and I allowed myself a little time to wallow and then the ups took over as, for me, Mastectomy was ridding the Cancer and the treatment following was about mopping up any stray cells.
It's a roller-coaster of emotions that dominate over the physical but in time I found it does get better.
I also had experienced caring Breast Surgeon and Oncologist who helped keep the emotions in tact along with their caring Breast care nurses.
Take care
Best wishes