I understand how you're feeling. It took me a few years not to feel apprehensive all the time, and I still feel that way some of the time.

Here's my advice:

1. Acceptance — "Of course I feel negative! I have f****** cancer. I don't need to beat mtself up for not being perky and optimistic all the time."

2. Separate feelings from reality - "The fact that I feel fatalistic doesn't mean something bad's going to happen. It's just a feeling I'm experiencing right now, and it will pass as new feelings arrive. I can't predict the future: it's not written yet."

3. Commit to leaving room for joy - "It's OK to let myself feel good sometimes even when I'm in a crappy situation. At the end of each day, I'll make a list of all my little moments of joy — a nice cup of coffee, a cuddle with a dog, a walk in the rain, listening to my favourite song — to help myself remember that they're always there."

Best of luck!