I was thinking about this as I did my usual bad habit, was wondering what yours are.
My primary one is touching the left stick when I really really want to be in one place. Usually happens when I’m SMG’ing someone to death, I’ll be scoped in and rapid firing, and my left thumb touches the left stick and eases me (usually) forward, or to the left, slowly. Not a good thing, throws off my aim and often takes me nearer to another enemy.
I yell at myself all the time about this thumb off the stick! but 1,000s of hours in I still do it.
The second one is a little more minor, but has gotten me in trouble. Running forward while reloading. I’ll clear a mob area, start running towards the next group that I know is ahead, and reload as I run. Usually ends up with the baddies spawning and starting to shoot me while I’m still in the middle of a reload. Again, I tell myself stop, reload, run but I still do it.