You will get better. My first Infinity Slayer match - 2 kills, 12 deaths - absolutely pathetic. Now, after playing for a while, I'm averaging 15-20 kills and about 9 deaths per game. That's still pretty crappy to most people, but I'm proud of the progress I've made in a week.
Stick with it, relax, adapt and just have fun. We all rage at the mistakes we make, but we learn from them, and we improve.