"Struggling with Consistency, Need Help" [src]
Consistency is one of the main problems players face when they start getting better. 'How can't I hit a thing today, but yesterday my aim was top-notch?' Counter-Strike is a game about variables, but so is life. Today you might be more tired than yesterday. You might've slept less, or maybe haven't had enough to eat. Generally people don't drink enough water. Keep yourself in good shape outside the game, and you'll definitely see the benefits in-game.
After installing Counter-Strike, most players just fiddle around with their sensitivity setting a bit, find one that feels moderately comfortable and then stick with it, giving it a small nudge now and again. This is all cool and dandy, but many a player tweaks their sensitivity mostly when they're not having a consistent day and their aim feels off. It's a bad practice to have, since now that you've fiddled your sensitivity on a bad day, it'll feel off the next time you have a good one.