One of the really great ideas that Rabbi Daniel Lapin wrote about in his book 'Thou Shall Prosper' was that practice doesn't make perfect.
I've heard from countless sources that 'practice makes perfect,' but I see many people practicing things for years and yet aren't perfect or even a master at it. There is some truth in that saying, but it should be re-quoted as 'what you practice makes perfect.'
What we work on indeed makes us better at doing it. But there is a huge difference between getting better at doing it and getting better in the skill. Take the sport golf; if you learn how to play incorrectly and practice doing it for 10,000 hours, you're going to be really good at playing incorrectly. I really like this example as it really shows that mastering a skill builds on what you already know; it doesn't grow. You can only do it faster and more consistently. Still, if you're not pushing to learn more, you will only do so at a very gradual level, and that's only because you are making small changes to get different outcomes, subconsciously.
It's what we practice that we will improve our performance in, not necessarily the skill itself.
Key takeaways:
1) Practice doesn't make perfect
2) Practice builds muscle memory, which allows you to do it faster and more consistently
3) You only grow if you seek growth