Learn to read the gameplay. I've played Crossfire a million times on COD4, so I know every single trick, where to throw nades, how to outflank someone if i know where they are, sneaky spots nobody looks etc..
I actually just finished a session and got accused of hacking twice
But the main thing is you need to have a mental image of how the enemy is moving. If they're coming up the right flank and your team is trying to hold them there, sneak around left and flank them. You just need to think a few steps ahead of the enemy.
And if you play with friends, work together. Set one up with an LMG or something to draw their attention. Then then they start firing at him, the rest pop up and kill them.
Just a few ideas for you, but if you really want to get better, practice, try new things, read online tips, watch videos.. but relax and enjoy the game. No point playing it if it's making you angry, trust me i've been there and it affected my relationships with other people. You don't want to go down that road.
You won't like it, but it is a game after all
Get good at real life things that will make you a career, then you'll be laughing when you're friends are still playing COD and you're out buying all sorts of ****.