Writing massive amounts of text also helps with self-estimation as a person who can write arbitrary amounts of text. My evolution as a writer started with me going "meh, I can't finish anything, I have all these ideas that I sometimes start but then I lose interest after a few pages". Then I started writing collaboratively with a friend, which was so much fun that I could say, "I like writing, at least of this kind, so much that I was on Utah time in Scotland to stay up and write more, for as much as seventeen hours straight." Then I wrote a finished novel... it was fanfiction, but I already considered worldbuilding my strength and character creation also on said list. Then I did it again. At some point I started being "a writer", who can decide to do things like "write a book" and have books exist as a result of this decision.
Followup to: Don't Fear Failure
In the same theme as the last article, I think that failure is actually pretty important in learning. Rationality needs data, and trying is a good source of it.
When you're trying to do something new, you probably won't be able to do it right the first time. Even if you obsess over it. Jeff Atwood is a programmer who says Quantity Always Trumps Quality
The people who tried more did better, even though they failed more too. Of course you shouldn't try to fail, but you shouldn't let the fear of it stop you from tyring.
I wouldn't go as far as to say that quantity always trumps quality, but where the cost of failure is low lots of failures that you pay attention to is a pretty good way of learning. You should hold off on proposing solutions, but you also need to get around to actually trying the proposed solution.
I'm normed such that I'll spend more time talking about if something will work than trying it out to see if it works. The problem is that if you don't know about something already, your thoughts about what will work aren't going to be particularly accurate. Trying something will very conclusively demonstrate if something works or not.
Note:
I originally had this as part of Don't Fear Failure, but that post got too long.