What keeps me going is usually praise, sounds lame and attention whoreish I know, but you don't make a MOD for 1 person you try to make something everyone will enjoy, at least I do...
The goal I set out for with X32I was to create a single player campaign telling a story, and trying to match retail game level of quality.
Why?
Because I'm not a huge fan of multiplayer mods :P, except a few like Zombie Panic. For the most part I like epic singleplayer games, and we need more epic singleplayer mods.
Past experiences with modding:
I made 2 square rooms in half life, and I made a corridor in UT2004...
Oh and I made gold pistol skin for max payne, though all was obviously for personal use ¬¬.
Crysis was what changed it for me, with my no modding experience and VERY small mapping experience it was a huge adjustment, and I spent many many hours messing around with the editor seeing what does what, then it moved onto the flash aspects to create new hud elements, to adjusting C++ code.
Hell I even make crappy 3d models now :P.
X32I:
X32I in it's infancy was BAD, and very different from what it was now, and even in the too early released demo version.
The only reason X32I came about because I was messing around with building parts in Crysis and managed to make a good looking wormhole and wormhole generator, and thought "hey... this could be awesome if I work on this some more".
Why I MOD:
Because I love games, and I want to create something which I can tell people "I made that" and feel proud of saying that.
Granted that did sound lame, but there's gotte be something I'm at least good at in this life :P.
Well that's all, not much of a blogger but wanted to share why I started modding, and why I do it.