The same is true, I've found, of writing in general. The more you write, the more you write.
To this end, I've set myself the task of writing 500 words a day (of the same manuscript!) for three months. This is a lot for me; usually I'm barely capable of writing a paragraph without going back and fiddling with the previous one. So it's sometimes hard work, but it's not as bonkers as NaNoWriMo's 1667 words a day for one month, and sometimes the day's wordcount is exceeded before I know it. And at the end of three months, if all goes well, I'll have 45,000 words, which is getting on for a Young Adult-length manuscript. Some, many or even all of those words may be utter pants, but they will exist, and this is but a first draft.
I learned long ago that I need deadlines to get anything done, and that even arbitrary, self-imposed deadlines will do the trick. Apparently I also need bribes like 'for every 15,000 words I will buy myself a present' and 'after 3 months I get to put it away and write a short story or something'.
It's very good for working through sticky bits that tempt you to leave it for a couple of days, which becomes a couple of weeks. I don't beat myself up if I miss a day, and so far I've been able to make up for low or zero wordcount days with high-verbage days later. Day Fifteen, one-sixth of the way through, and I should be on 7,500 words by close of play tonight. I hit 8,500 before I left for work.
It's all going suspiciously well so far. If I never speak of this project again, you may draw your own conclusions.