I know there's an argument that if your stuff no longer inspires you, if the act of writing becomes weary stale flat and unprofitable, if every line you write says Bad bad bad why do you even bother???- then you must write more, and constantly, until you get over it. Keep swinging at those balls, as the metaphor has it, and eventually you may hit one again. I'm just not sure it works. To churn out one uninspired piece after the other produces, in me, nothing but depression. When you reach your limits in one direction, why go on trying to advance? You may not have hit a temporary obstruction: you may have hit twenty-mile thick rockface.
It's a balance of miseries. Which is worse, not writing or writing badly? For me it's writing badly. And at that point I think it time to stop and do something else- in my case read or translate or study the primitive forms of Chinese characters. Quod uides perisse perditum ducas- cut your losses. And- ahhh! go read the new chapter of Phantom Moon Tower that kickinpants has just sent me. See? There is life after fic.
ETA: you know that one about the good being the enemy of the best? I think something like that's partly behind my uneasiness with 'the next one will knock them dead.' If you're reader-focussed, and focussed on pleasing or wowing your readers-- well, you're not aiming at anyone who'll give you a hard time if you fail to produce the best, are you? If people like your work what they want of you is more. They may well be unhappy with anything new and different, or to see you fumbling with a new genre or new techniques that you may not have mastered yet. You see it happen all the time with singers. Most fans want the old standbys and don't want to hear the new tunes the artist is working out or on. Same with 'I love your stuff!' IME it often means 'I like this kind of story- even, this fandom or this pairing- so don't write any other kind.' In the end, who's going to keep you honest about the quality of your work if not you?