playing first person shooters is impossible with an external mouse.
And now we come to the revelation. Every game I play, everything, is played with the touchpad on a laptop. My fingers dance across the touch pad, the smallest of adjustments to the most grandiose movements. Trying to play games with an external mouse, for me, is like pulling teeth. There is something incredibly disconnected and "impersonal" about using an external mouse. Theirs no "feel" to the actions performed on the screen with this backup mouse. It's almost like I move the mouse, and someone next to me has the real mouse and is trying to move it in the exact same way as I move my fake one.
TL;DR, I can't use an external mouse.