Switch to Decaf coffee. Seriously, though, I think I remember from your intro thread that you wer 11. Your hand will get steadier as you get a little older and get more practice. Then you get old and it goes down hill again. Now I know you don't want to hear "wait til you grow some more" (you probably hear that enough on other things) Here's how I do it. Hold the piece you are painting against something big and flat, like the top of your workspace. Put your painting arm against the edge of the table about 1/2 way between your wrist and elbow. Lay your arm over to the piece and rest the edge of your hand (where your pinky is against the table top. Now you are using most of your arm to steady itself. You will still shake a little, but it will reduce a lot of it.

Here's a pic of it:


I usually hold the piece with my other hand, but it's hard to take a picture with both hands full. You get the idea.

I am fifty five and never done better work .....
Arthur