I totally agree with you, for me it's the euphoria of seeing it work, after days or weeks of poking and reading and prodding and reading some more and scratching your head and re-reading the same things.

That light-bulb moment is addicting, that's what keeps me going.

Edit: There also seems to be a little bit of correlation between how long it takes to make it work, and how great it feels seeing it finally do it's thing. That can be a source of encouragement to take on a project that's a bigger than your previous one.

Being the 21-year-old guy who didn't learn how to ride a bike when growing up I am, this has actually motivated me to do exactly that, as a start.