A same object, no matter what its texture, will look completely different under various lights. I always remind myself that the eye never sees the object itself, only the light that bounces off it. That's my 'secret'. I bought the software, read a few books, a few tutorials, talked to a lot of artists, and got my feet wet. Technique, at least to me, is not as important as expression.
Technique is a tool, nothing more.
I keep at it, try again and again, and eventually I get it right. Too many people worry too much about technique and forget they bought the software to express and enjoy themselves first. I focus on my message, what I want to express, the technique comes by itself. Just relax, find something deep within you that you would like to share with others, and paint it. Let your technique grow by itself under the light of your heart.