Though you should be plenty attentive to quality, you also need to keep your output up. Take a look at Bob Dylan—massive numbers of records and songs, of which many became legendary. Similarly, see Seth Godin’s collection of over a dozen books and a daily blog—constant creation. The Beatles performed live so many times that it’s hard to quantify how much practice they got, and it made them much, much better. The point is that you have some ideas you want to push to completion, and one at a time, you should churn them out the best you can.
(For the books you want to create: remember that you can always create a better second edition.)