Killing an enemy right away isn’t always a good thing to do. Sometimes it’s hard to contain yourself. But self-control in a game like CSGO always gives you good results.
If you walked into the enemy’s back, or if he passed you by without noticing your position, don’t be in a hurry to kill him. He won’t give information to his allies, so they won’t expect to find you where you are. This is a simple way to kill two or even three enemies covertly.