I was sceptical when I first stepped into the land of Lordran and perished at the hands of yet another undead nightmare hunting me, for I assume I'd angered it in some way. I do not know what I did to annoy this poor hollowed creature but it wanted my blood so I unburdened it of the strange life force causing it to attack me so. I had already died to it many times but this time I managed to vanquish the foe and move on...
...to the next foe and subsequently die at its cold hands. This pattern repeated itself for quite a while until finally I managed to defeat the Asylum Demon and escape that wretched place.
There was something magical about that experience that, now that I've finished the game a few times, I thought I'd never get back. Something part encouraging, like making progress in a puzzle; and part infuriating, repeating the same part over and over again, but I knew that the game was not at fault. It was me, I had to change my approach. Maybe switch out my equipment or take things slowly.
A great design of the game which I'm sure is deliberate is preying on human nature where, for example in video games, we encounter something difficult, only to fail at completing the task; we rush in recklessly only to fail again. The more we try the more frustrated we become and the worse we play. Dark Souls forces you to take a few minutes, calm down and think about the situation: is rushing in head on really the best solution, maybe I should draw the enemies closer to me one at a time and pick them off, maybe I should get my bow out and snipe, wearing the group down until I can pass through.
This is compounded by the bonfire system which respawns every1 enemy and forces us to improve our play. We will not get any better by "saving" our progress at the nearest bonfire. My favourite example of this is the spell system. You have only a limited number of casts. To get more you need to rest at the bonfire, but this will respawn the enemies so you have to learn to be more efficient with your spells.
Towards the end of my spell of playing the game I was getting complacent. I knew the enemies well and could predict their actions. I would still die to the stupidest things, or unfortunate circumstances, I was not amazing at the game, just sufficient, but I felt strong. Worthy of defeating this game widely acknowledged for its difficulty. I had lost the magic that I felt at first when I played it many months ago.
Since then I took a break. Not deliberately: other games came and went, and other commitments had to take priority.
A few months went by and I got curious. Could I still play the game as well as I used to? Is it like riding a bike - once you learn you never lose the knack?
I suck again, dying to the first few hollows I encountered. I'm currently stuck again at the Parish and that feeling of inadequacy is rushing back to me, where the game is most magical. If there's no challenge to overcome then are you really playing the right game?
I've started watching speed runs of the game and this seems an amazing way to keep the PvE section of the game new and fresh. I delight in telling people that my first playthrough took around 50 hours, and some people can complete it in less than 1. PvP is the other way to sustain this game for players: generally being a dick and invading poor helpless beginners in Anor Londo (more likely someone in dark Anor Londo just waiting for fresh meat, or someone on NG+), the PvP arenas in the Township, or invading in common PvP zones. For a game with no communication beyond predetermined messages and gestures it's surprisingly easy to convey emotion.
I genuinely believe that Dark Souls is one of the best games I've played, with amazing amounts of depth if you search for it. Check out EpicNameBro's amazing lore series, or VaatiVidya's Prepare To Cry series for lore discussion, UberGoose's speedrunning to see just how much possibility there is for extending the game.
The depth to the character build system is immense, the range of techniques that you can employ are diverse and always fun. Create a sorcerer only build, using magic only. Or set yourself some challenges like (my current build) a no-shield run2. This will teach yourself to dodge effectively as endorsed by Vageta311, check out his amazing Everything possible before the gargoyles series for a real eye-opener to the game and just how much is possible.
Alternatively take a break for a few months. Let your ability die down and regain that magic for yourself.