The hardest & best things about writing?

So what IS the hardest thing about writing? Is it the deadlines? the endless word counts? the commitment to productivity and (hopefully!) quality? Is it the low pay? the long hours? the frustrations? Let's flip the question: what's the best thing about writing?
I'm going to answer this second question. The first question doesn't appeal to me as much! FunCreativeDifficult, hence stimulating and endlessly fascinatingAlways learning something newGet to play with...