MOUSE SETTINGS

Go to mouse settings (windows, not in-game) hit additional mouse settings, pointer options. Now.. turn off "Enhance pointer precision". TLDR about this - windows inputs random numbers that makes your mouse speed up and slow down etc, and this is extremely INCONSISTENT.

Colors

If you look at some of the former CSGO players, you'll notice their game is more colorful.. this is the "Digital Vibrance" setting. On some monitors it's called Saturation. Too much saturation can strain the eyes though. But having this setting on a bit higher will make enemies "pop" out more; especially since this game has outlines. (Wardell uses yellow, and this is the first color the human eye catches first btw).

Crosshair concepts

You want a crosshair that doesn't block vision of people from afar, so you'll see players run "dot" crosshairs or have a gap big enough to see. But if you dive deeper some players will agree that if there is a gap, you are actually aiming with your eyes rather than focusing onto your crosshair. Again it's down to preference, but having a gap, and the tip of the crosshair to "assist" with sprays is great.

Running and gunning

Simply let go of the direction you are moving and tap the opposite direction to "stop" faster.

Too much time in range, or with weapons that don't really matter.

Example.. your most used pistol in econ rounds? Run and gun ghost is actually insane. Classic burst is good too. I highly doubt players use stinger in their "range" warm ups or death match.

One of my quickest climbs in CSGO was when I was goofing around with Deagle only... it taught me how to really predict where people are moving and the effects of 1 tapping people does to them. That and you can buy your team guns by running Sheriff/Stinger/Bucky only. (You have 7k, buy your team Operators and they will love you and actually try to win).

Eye strain

Take breaks, hot shower, stretch for a few minutes.. but for me if you go outside and focus on objects that are far away helped me the most.