Ernie hit it right on the head.

Practice does not make perfect. Perfect practice makes perfect.

If there are some fundamental things that may be lacking in your form or execution, you can only get so close to your goal before peaking out. Use good fundamentals and you will improve markedly.

When I shot competition archery, I was able to shoot about 289 (of 300) as my personal best. When I had a bad day, that dropped to the mid 260s. It didn't matter how much I practiced, or how aggressively I spend on equipment.
With the help of a coach I fixed a number of things I was doing wrong and my scores dropped again, down to the 240's. But when they started coming back up, they just kept going and going. Now, the more I practiced, the better my scores got. When it did have that "bad day" it was a 2-3 point drop over my average vs. a 20 point drop. Eventually I held a 300 average for most of the season.

Using my old form and techniques, I would never have been able to achieve that elusive 300, regardless of how hard I practiced.

I would be willing to bet that all of us on this board would benefit from time spent with an experienced coach. There is only so much you can learn form internet forums and youtube videos.