To begin with, no matter how much you train, the only way to reach the eight sense is to die. Only then it activates, so if you aren't capable of doing it... You become just another tortured soul. And even if you activate it, if you die you can't return to life. I'm not sure if you could return to the living world as a ghost, though.

There's a way to activate the eight sense without really dying, if one uses one of the passages that connect the living world to there. But if you can't activate it you will die either way, if do activate it, though, you will be free to roam that place and return to the living world in your living body. It's useful, but only under specific circumstances and it's a risky bet.