Surround yourself with people who make you feel good. Don't shut out your family, especially children. Think about all you have to live for. It's important to know what's important to you. Insist on a doctor you trust.
Nobody really knows much about breast cancer.
Try anything that might help. Expectations influence outcome. The human body is a miraculous healing machine. A one-breasted body isn't ugly, just different. Losing a breast doesn't have to affect your sex life.