Here is some unsolicited and probably poor advice about painting and otherwise everything I learned in art school:
Painting is just as much of a three-dimensional art as sculpture. Paint has form, body, weight, and dramatic physical composition. Don’t just think of it as color or pigment, think of the paint as a sculptable material you’re building up on a flat surface.
Work backwards, always. That means working from the background to the foreground but also working your colors backwards, too. Start with white to get light blue, don’t start with blue and add white to get light blue. Subtlety is key.
When you’re first buying paints don’t stress about getting every hue and pigment. Get a titanium white, ultramarine blue, cadmium red medium, and cadmium yellow medium. And maybe Naples yellow because that shit is hard to match. Everything else can be mixed (unless you’re going for some extreme neons, or dioxin violet or whatever).
Painting involves just as much erasing and stepping backwards as drawing. Or typing. Go all the way and then scale it back by 20%. That thing you did in the corner, that line or shade or highlight that you really like? Paint over it. Do it again. Recreate it. Learn what you did to make it happen in the first place and commit that lovely line to memory. Do it a few times before you let it stick, before you leave it alone.
The painting is done before you think it’s done. Let it sit. You will be 80% through and then you take a break. Come back an hour or day or week later. Stare at it with a cup of coffee in hand. Close an eye. Look at it backwards in a mirror. It’s done.
Never ask your friends to critique your work, unless they are strongly opinionated and lack a tendency to tell you what you want to hear. Unless your significant other is an artist or creative type don’t ask them what they think because they love you and will tell you it’s brilliant even when maybe it’s not. Sometimes that’s okay, and necessary, but it may not be what you need to help you improve your work.
Whatever you didn’t accomplish in this painting, you will address in the next.
The best artists are those that do other things with their lives so they have stuff to make art about.
Don’t take yourself too seriously.
Keep sight of what made you fall in love in the first place.
This might all be terrible advice.