TDLR: Don't make my mistake. Slow down, work at a consistent, relaxed pace, and treat every tool like it can kill you.
I think a common mistake many people make is to be more careless with some of the less notorious tools (drills, sanders, handsaws, etc.) than the table saws of the world. That happened to me with a belt sander. I'm no professional woodwork, so was using a combination of hand planes and my belt sander to flatten a large tabletop that I over-clamped during glue up. Working with headphones and a facemask on, I had been sanding the top down with 80 grit for a good 30 minutes. I turned off the belt sander and wanted to check the paper. With my headphones blasting music, I couldn't hear that it was still spinning, so instead of waiting a few additional seconds for it to completely stop, I inadvertently touched the paper while it was slowing to a stop. The sander instantly pulled my finger into it, leaving the damage you see here.
Safety is super important to me (I know, right), so I was extremely disappointed in myself for doing something so careless. I've pinpointed the "why" to a combination of bad habits and rushing.
I got in the habit of touching the paper on my orbital sander while it is winding down. I'm still trying to break that habit ... just caught myself touching the orbital paper while winding down when sanding drywall last week. Bad habits are tough to break, especially when you only have a couple of free hours to spend in the shop, but I'm actively trying to incorporate Michael Pekovich's rule, Don't Rush, But Don't Stand Still: "Find a tempo where you feel as though you're moving at a constant pace from task to task, a tempo that allows you to invest the necessary focus for each task without feeling as if you are rushing though some tasks and hitting a wall with others ... The important thing is you always feel in control of the process and of the quality of work you are doing"