First, just take a deep breath and pause. Always make time for yourself. Don't be afraid to feel the emotions. Instead, experience them. Experiencing the fear and the pain somehow makes it feel like it's not bigger than you are. I also firmly believe God never gives me more than I can handle. Sometimes I question his judgement, but I do believe I can get through it.
I also feel journaling is very beneficial. It really helps to get the negative thoughts out and then your mind can be filled with positive thoughts and an attitude towards beating the disease.