The worse thing that can happen to you is lose a bunch of souls and humanity when you need to use them.
No, the worst thing that can happen is that I have to replay about half an hour's worth of the same exact thing I just did. And that quits being very fun, very fast.
Dark Souls' challenge comes from figuring out how to deal with the obstacles it throws at you. Learning the maps. Learning the enemy attack patterns. Once you /know/ what you're dealing with and how to beat a given enemy, there's not much difficulty in actually executing whatever sequence of actions you're supposed to do.
Nothing actually changes in how you're going to do this.
You don't so much get good at Dark Souls as you memorize how to do a given stretch of it without dying.
For any given stretch of map, you are going to learn where the enemies are, how they attack, where you're safe, where you get ambushed... you're going to learn that really fast. And you're going to repeat the sections you already know how to do when you die, which isn't fun, because they're no longer challenging -- because you're no longer figuring anything new out. But you still have to do them, and they don't go by that fast.
The fun part of Dark Souls is figuring out how to beat the hard parts, but the easy parts start outweighing the difficult, interesting parts pretty fast, and you have to keep repeating the easy parts to get back to the hard parts.
And that's tedious.