During training, training like 'hajime' practice and other training, we are often told to train with the mindset that we would die if we stopped...shinken shobu...train like you are in a sword duel to the death. While not actually facing life or death situations in a dojo, I feel like this development can still take place as your subconscious isn't aware if you are actually in mortal danger in the dojo.
Yes, although I think many people would misread this and think it's a game of "let's pretend", of trying to suspend disbelief. That's not it -- those games are matters of conscious thought. I am not sure how you cultivate this subconscious perception you're talking about, but in my limited experience it depends on the conviction that your training partners bring to practice.
I used to study shindo muso ryu jodo - jo vs. sword, the jo always wins. Or it's supposed to. In our practice, reishiki and correct form when ending the kata and withdrawing were at least as important as the kata itself, and my sensei was quite strict about this. One night we were practicing, me with jo and him with sword, and I made a mistake in withdrawing. He told me not to do it, but (I was very fuzzy-headed that night) on the next repetition of the kata, I made the same exact mistake -- basically withdrew my jo before he was out of range. The instant I started to make that motion, two things happened. I had the thought, with total conviction, "I'm dead" -- in a very literal sense, not meaning "I screwed up," but a complete and total certainty that I had just made a fatal mistake and was now going to die. And, as I thought that, my sensei stuck, full speed and full force. His strike stopped a millimeter, if that, from my ribs.
It is so hard to explain or analyze what happened. Did my conscious mind believe that he would harm me? Of course not. But my subconscious mind was completely convinced that I had just made a fatal mistake, and that whether I lived or died in this moment was entirely up to my opponent.
Guess which mind was right?
It's a memory that I cherish. I also think, in some ways, that that experience is antithetical to the type of "training" that I sometimes hear described for "dealing with fear". I know that I noodge constantly about clarification of terms, but this one is as important as any. When people talk about "dealing with fear" as a goal, most of them really are trying to restore their mental comfort -- and the only way to do that is to convince yourself, rightly or wrongly, that there is no threat. You cannot be in a true state of fear and be comfortable in it -- repeated subjection to those conditions is one of the ways that PTSD happens (and PTSD is a normal reaction of a normal, mentally healthy individual to an abnormal situation). The solution to fear is to eliminate it, and there are healthy and unhealthy ways to do that.