Feeling jittery

Has anyone got any good tips on coping with the fear we must all feel inside? I am trying hard to stay positive, but knowing my tumour was very large and 5/13 lymph nodes were infected, I am terrified for the future. I had a lumpectomy, but the margins weren't clear, so they are going to start chemo first ( I see the oncologist on Monday) and after chemo they will do a mastectomy. If it had been a small lump and they had got it all I would feel more positive, but I can't shake off this terror inside. My scans were clear which I know is a positive, but if anyone else has been in a similar position with a good outcome I would love to hear from you.