This advice reminds me of an anecdote from Art and Fear [1]. A ceramics teacher divided his classes into two groups. One group he told would be judged only based on the quality of the best pot they made, the other group would be graded based only on the number of pots they made. After the two classes had finished, the teacher noticed that all of the highest qualities works came from the class that was aiming only for quantity. It seems, at least for artistic/creative activities, simply diving in and making lots of attempts is the key to rapid improvement.

[1]: https://www.goodreads.com/book/show/187633.Art_and_Fear?from...