Mouse sensitivity, that is. From here onwards just “sens”, because it’s a pain in the arse to type out the whole thing.
Anyway, question of the century: “What sens am I supposed to be using?”
Guess what, it doesn’t matter a single bit.
What does matter is that you pick one and stick with it.
Alright then, so how do you get good at aiming?
Well, how do you get good at throwing a basket ball into a net? That’s right, you practise. What exactly are you practising though? “How hard to throw the ball?”, you may jokingly reply. Yes, that is exactly it. You train your muscles to remember how much force to put into throwing the ball, so that it lands exactly where you want it to land (just in an attempt to be scientifically correct; it’s not your muscles that remember – the memory is still in your brains, but it is memory for the muscles).
The very same principle applies to mouse movement – you move your mouse to exactly where you want it, because you have trained your muscles to remember how much force to put onto your mouse. And of course you can only train this properly if your mouse sensitivity doesn’t ever change.
Muscle memory, one of the greatest things about being human.