Too be honest, I'm more likely to quit after a hard boss. I don't like being beaten, and I keep working until I overcome whatever was holding me back.
But then I look back at everything I did, and look forward to all I have left to do, and I can't help but think "It is so not going to be worth doing this again". So I quit. Even though I may have a nice, leisurely trip to the next boss ahead of me. I don't care anymore.
Whatever engagement or attachment I have to the story is thrown away when I have to repeat a section of it ad nauseam. I wind up wondering why I am even playing the game. I beat the boss, I feel happy for a few minutes, but I've lost any forward momentum in the plot. I've lost dozens of hours of my life for this fleeting satisfaction, AND I HAVE TO DO IT ALL OVER AGAIN IN AN HOUR OR TWO.
No. Just no.
The one time I have actually felt a sense of lasting accomplishment from winning a difficult battle, it was an optional superboss that I took on, on my own terms, and I defeated, just to prove a point. Doing that to progress? The satisfaction wouldn't last. What is the point of going "oh, I beat the first boss" after dozens of hours of preparation, when all it gets you is "great, here's 55 more"?
Dark Souls was one of the worst game purchases I ever made. I've literally never even turned the game on. I see no reason to. I've seen people play, I've seen screenshots, and there is nothing that makes me think "oh, wow, I'd love to try that", or "ooh, I wonder what's over that hill". I see no reason to explore the world, no reason to quest in it, no characters to care about, nothing to get attached to. I picked it up on a sale and I'm still kicking myself about wasting that money.
I don't give a damn about game challenge, I want more. You can deliver challenging gameplay and a satisfying rest of the game (see anything in the Shin Megami Tensei series). But they are very rare compared to the games that are just difficult and nothing else.