I found this book in the local library and couldn't put it down! It's called "101 Things to Learn in Art School".
Now I've always been hesitant to pay much attention to people telling me how to create art, but there's a lot of wisdom in this book. Some of the ideas it explains (each lesson is on one small page, boiled down to it's basic premise).
Your art needs to look good at 15 inches and 15 feet. If it doesn't, then you should keep working on it.
Nobody cares if you have mitigating circumstances in your art - "I tried so hard on this piece; or I painted it at a painful point in my life", etc. You won't be around to explain your special circumstances to viewers, 99% of the time, so it must stand on it's own.
You have to master the techniques you are using. A poorly executed piece or art based on a great idea or image doesn't necessarilly succeed.
There are so many other great bits of advice I pulled from this book; I'm feeling i need to purchase a copy for reference.
Todd