@Neo Zero Sakurai on Dark Souls, originally from a Famitsu coloumn:
"It's a game with the sort of difficulty level where you're killed instantly if you let your guard down," he wrote. " Every mistake causes you to pay a severe penalty. You're constantly watching out for back attacks and pincer attacks, always tapping on stone bridges before you cross them. Every corner you come across takes on vital meaning. What if there's some foe I can't defeat on the other side? Should I try not to make any sound? Am I all right on stamina? What if there are enemies on both sides? Anything behind me right now? And so on, and so on."
Sakurai went on to note that this extreme difficulty is tolerable -- enjoyable, even -- because of the rules the game world follows. "There are bonfires throughout the game that refill your life to maximum," he explained, "but if you use them, all enemy positions are reset. In other words, you're traveling from a bonfire to the boss, or to another bonfire, and that's the equivalent of a 'round' in the game. You also have Est flasks which can be filled for 5 uses (later 10) at bonfires. If you feel like you're short on Est, you can either turn back or keep going. It's an item that inherently forces you to make a strategic decision during each 'round' of play."
Once he got used to this, Sakurai found it relatively easy to proceed along. Then problems popped up. "There's an important item, called a Fire Keeper Soul, that enhances the effect of Est flasks," he said. "I was having trouble against this butterfly-shaped boss, so I was looking around for items that could help me. So I found this item and used it...but nothing seemed to happen. It raised the Humanity stat, but nothing else. Going back to the start point, I realized that you're supposed to offer the Fire Keeper Soul to a certain person in order to permanently power up your Est flask. This game runs on autosave, of course, so it was too late for that -- I had wasted a golden opportunity."