Spending days working on a map, then reaching that point where you realise it's just not working... which is about 99% of anything I've ever done in wc/hammer.
But at least I know when to quit, instead of releasing half finished, ill thought out crap that nobody will play. (rjump_bliss being the only exception
)
tbh it's hard to get anything done when you're your own worst critic... I scrap everything I make... abandon maps left, right and center... mapping consumes so much time and produces so little (at least with my planning/workflow).
Oh and Steam... I f*cking hate having to put up with Steams mood-swings... give me stand-alone apps any day.