Quantity over Quality
Let's say it one more time for the overachievers up in the front: “Quality over Quantity” is for consumption not creation. When you are choosing what to bring into your life it makes sense to be choosy. When you are working on your output you need to just keep producing. Writing 200 words a day is a far better practice than fretting over a thousand words for a week. “Thinking about writing” doesn't make you a better writer. Writing does. The only way to write the things you're really proud of is to write a whole lot of other stuff as well.
We accept this in some areas easier than in others. In performance-based arts we accept that rehearsals aren't going to be great, and that we need to just keep putting in the time before the performance. But it's harder to accept when each “practice” is also considered a performance. There is rarely a record of how good or bad a specific play rehearsal went, there is almost always a record of our writing practice, unless you're far better at deleting things than I am. Maybe you are. Or maybe it would be better if every play practice were recorded, so the actors could sort through what went well and what didn't, and more easily pick out the things that worked from the rest of the session.
But even this stems from a deeper problem. We have somehow decided that “worth” is equal to “output”. The value in practice is not what you are creating, it's in what you are becoming. It's in how you are changing. If I am diligent in becoming a good photographer I will take a great many pictures, and the natural function of this is that I will, at some point, take some great pictures (and do all the other things that photographers do that I don't understand) that I can sell or put in a gallery or what have you. If I keep writing (#amwriting) then the natural outcome is that I will eventually write something good enough to get me some recognition. But it can't happen without consistent effort.
I write a story every week, because it's impossible for someone to write fifty-two bad stories in a row.
-Ray Bradbury