When I was 18 I had all my hair, and long at back's lenght. One day, using the drill, my hair got tangled with it. Luckily, it was not at full power, I had it switched off but with the spinning momentum it rolled up to my head. It was painful, and removing the hair from it was difficult and embarrassing.
There is something I'm over-zealous with: safety glasses. I don't use the dremel tool, grinder or drill without them. I can deal with cuts, bruises and scars, but the last thing I want is to loss one eye when you can avoid it.
Raul