Look at it this way. You're in the studio and you make five paintings a year. Those have to be the best five paintings you can make. They have to be excellent. No mistakes. No crappy composition.
How likely is that? What level of skill does that take? Well, it's not very likely and it's a damned high level of skill.
But what if you create five hundred paintings a year, or even fifty? You have that many more chances to get the good stuff. I really believe this.
If you are a major league baseball player, you take batting practice every day. You look at a lot of pitches. You swing the bat hundreds of times. Sometimes you get on base, sometimes you strike out. And sometimes you hit the ball outta the park. Grand slam homer. Your batting average goes up and when contract times comes around, you may just get more zeros in your check.
Now you're an artist and you want to get better, right? Paint, paint, paint. Get in the studio and paint. Then go to the museum or gallery and look at paintings. Hang out with your painter friends and talk about painting. Take a painting by your favorite artist and reverse-engineer it. Figure out how he/she painted it. Starting from the ground up. Copy it faithfully. Not one time, twenty times.
Do you think Michelangelo drew David one time and got it?
Do a lot of work and you will get better. It's just that simple.
It's the numbers.