If you are easily frustrated, you may as well just move along, because you'll want no part of the PS3 exclusive, Demon's Souls. Even if you're not-so-easily frustrated, you may want to reconsider going anywhere near it. It's a brilliant, exquisitely crafted action RPG, one of the most unusual and rewarding gaming experiences currently available, but make no mistake: This game wants to make you cry. Not in a death of Aeris kind of way, but in a school bully kind of way.
The tone of Demon's Souls is set at the end of its tutorial, when it kills you. Your soul is then sent to the Nexus, which serves as a hub for the different areas you'll visit in your quest to rid the world of demons. The denizens of the Nexus are a pessimistic lot, with most of them telling you that you're about to die. This isn't hyperbole for the sake of storytelling, this is an accurate analysis of the game you're about to play. You will die, and die a lot, and if you're not OK with that, you should probably just move on.
Dying isn't the hardship you'd expect it to be, though; as Miracle Max might say, you're only mostly dead. You can still do everything you could when you were alive, you just have less health at your disposal. Your health bar is permanently depleted at least one quarter (by half until you find a Cling Ring), and can only be completely restored if you earn your body back. Fortunately, killing the boss at the end of a level will restore your corporeal form. Unfortunately, getting to said boss and encouraging it to shuffle off the mortal coil is a somewhat Herculean task. Each level is littered with traps, falls, and enemies, many of which can kill you with a single stroke. The bosses themselves are enormous but, ironically, their straightforward nature usually makes them far less stressful than the legions of monsters that came before them.
Demon's Souls is more than a little roguelike by nature; when you die, you lose the souls you've collected by killing enemies (you get to keep your items, though) and return to the start of the level. It can be incredibly frustrating, but as punishing as Demon's Souls may be, it's also fair. If you can make it back to the bloodstain marking the spot where you died, you get your souls back. As you make your way through the level, you'll also open doors and flip switches that will help create shortcuts from the starting point to areas deeper within in the level. Enemies will regenerate, but once a door is open, it stays open, a fact you'll undoubtedly appreciate the fourth, fifth, or tenth time you attempt to clear an area.