Alright. I've made a deal with myself: if I cut again, I'll try to get help.

Deeply and dangerously aren't simultaneous as in that I only cut the fleshy bits of my body, which tend to lack veins and tendons.
The part that mostly shocked me about the deeply - and told me something was seriously wrong with me - was when I was looking at a cut with a centimer (0.4 inch) distance between the edges.

Thanks for your last post, IWonderIf. It gave me some insight and made me think.