All my students know that I'm big on mileage. You have to paint a lot to be good at it as in most things in life. Yes, you can have a knack for it, but there's no real substitute for doing it. But putting in mileage doesn't have to mean that you dive in willy nilly and just put product down on a surface. And it doesn't mean that you paint just anything. I think that your mileage has to be very thoughtful and even careful at times. Being a really good painter means orchestrating your painting; having a focal point, directing your viewer there. This takes a combination of nuance and then hitting some passages hard and with authority. It means choosing your subject matter carefully, making sure it's something that enchants you. If it enchants you, likely your viewer will be too.
I'm working on a piece today that requires patience and nuance. This piece is all about the gesture of the trees and their relationship to one another, how they are dancing together. So a lot comes down to drawing. What is is front, what is behind, which branches are lost and found? How does the light dance between the trees? What are all the spaces between? I changed the shape of the tree trunks and the branches a bit from the reference to get the gesture that I wanted. There are several relationships going on here within the painting. The main tree shape,(lighter in value) and it's relationship to the background woods and then the darker branches reaching in from right side.