Somthing that can really help you out and encourage you, is to think that this is a real situation. If you get shot your dead. You treat the game as if it were real. This always makes you think a lot better and help you conscentrate with your accuaracy, and tactics.
Say you see two people and you have a shot at either of the two. You shoot not thinking at all you miss they find you BAM! your done. Now on the other hand you think. This is it, if I miss I am dead. It kind of fun accually. This will make you a bit more accuarate because the shot is important to you now and you REALLY don't want to miss.
Hey it's what I do, try it out it might make you think better or somthing.