One thing that's never a good response to any adverse circumstance is the "Why Me" attitude. It's self-defeating, and it won't help you to deal with this life-struggle that you have just unwillingly begun.
You didn't get cancer because the world hates you, or you needed to be taught a lesson - it just happens. There's no cosmic revenge involved. And, if you didn't know it by now, self-pity, no matter what the situation, isn't going to help you one little bit. It also has the effect of alienating others if you're a continual "drama queen" about your life. I know that I find people with this kind of behavior incredibly draining and tiresome.
Reading and educating yourself as much as possible about your cancer is a good way for you to focus, and push away some of your fears. For example, I read "Dr. Susan Love's Breast Book" from cover to cover immediately after my stereotactic biopsy, prior to my diagnosis. I wanted to know my treatment options, learn about possible surgical procedures that I might have to consider, and it was important to get this type of information from a renowned physician in the field. When I got to the part about various reconstructive surgeries, I actually began to feel sick at this possibility, but I kept on reading. Luckily, I didn't need this type of surgery; but it made me realize that there is always someone who is facing far more than you are, and you need to keep this in perspective. Your life is literally in your hands; you must be well-informed about your situation and the decisions you need to make. An educated patient is an effective self-advocate. Your focus should be on using your energy positively, not negatively - don't waste it feeling sorry for yourself. You don't have the "luxury of time". Don't let your diagnosis stun you into a state where you're unable to take action. Harsh advice, but true.