I'll have to agree with JJ on this one. It's aim and a desire to get better. If you are losing or not doing as well as you would like then there must be a reason, so figure it out and work on that aspect of your game. Learning from mistakes and using that to help improve your game is a lot better than complaining because you refuse to accept that you are making them. Play smart, too.
If you want to work your aim then use something that fires slow and requires that you aim at the head, such as the anaconda or 93r on burst or m16. Because either you will aim at their head and kill them or be raped. It might not be pretty at first but over time it will help a ton as far as aim is involved. There are a lot of little things that one could do to improve at games but generally they are just things pick up over time and from playing with good players. Hope that helps some!
- Sactasm [moosik!] / [$aC]Ghosteh[eG]