Others have this mostly covered it seems, but I'd add: it's easy to get discouraged when you start a painting, because everything looks rough, flat, and badly-p

Others have this mostly covered it seems, but I'd add: it's easy to get discouraged when you start a painting, because everything looks rough, flat, and badly-proportioned. A lot of people tend to give up there, but the trick is to keep putting down more paint. Paintings by talented artists look the same as a bad sketch when they first start and only have one layer of paint down, but by the time a good-looking painting is done there are many layers of paint on it.