Painting and observing directly from life is the best way to learn to paint, but studying other paintings is essential also. Knowledge about painting and technique has been handed down through history so there's no sense in re-inventing the wheel. Study paintings to see how other artists simplify shapes or how heavy or thin they apply the paint is helpful in developing your own view of nature. Don't study just one artist, but as many as you can. Look at how they treat edges, hard or soft. Look at how they see color, do they push temperature contrast or emphasize muted color harmony.
Studying the way other artists deal with composition is helpful too, or how they deal with detail. I think that's why I enjoy looking at certain paintings, they have solved problems I struggled with. So don't try to re-invent the wheel, with the internet an infinite number of good and bad examples are at your disposal.