So in order to get things started I thought I just do a sketch first, for my eyes only. I got the idea while reading "Daring Adventures in Paint" by Mati Rose McDonough (highly recommended). Mati Rose writes about making a sketch first and then transferring it to whatever you want to paint on. I was hoping that this would take away some of the fears I had - and it did.
So I first made a rough sketch of a mermaid - just drew it on regular computer paper (this is how I use up paper that is printed only on one side).