Quake (back when) did this to me.
I would play some, and it was too hard for me, as I am deathly badly coordinated for FPS and I couldn't get far, and it just seemed I was spinning my wheels on it.
However, I then had some damn burr in my buttocks (I think it was the left cheek, not sure, been a while) and I decided that I was GOING to finish that damn game. And do it on Hard. Because I am nothing but a masochist when I'm determined (see Brawling Humiliator in CoH) and Nightmare? Yeah. I knew that wasn't going to work. Hard it is.
And I did it. I just, every night, played through a level or two until I got it done.
Took *forever*. Well it seemed like it. But the 'Hell yeah!' I gave myself when I gibbed Shub?
Totally awesome feeling.
And then I realized... it's over. Aw. Dammit. Now what.
(Quake 2, and 3, of course. Never finshed Quake 4, just... lost interest by then, CoH was out, and that was that.)