You have the same problem I did. I would swear I have ADHD. so what I do is look at my books or patterns until something grabs me. I take a picture of a quilt (if possible) and instructions on cutting and piecing the block. I take a little swatch of the fabrics I choose and glue to to one of the block patterns. Then I take out the book and go directly to work on what I have chosen. As new ideas come to me, I keep a book near by and jot down the idea for future projects.
The other secret that I have found is to make "Scrappy" quilts--a jumble of colors and patterns without worrying about harmonizing. The quilts are really beautiful.
Just make yourself concentrate on the project at hand.
Lucille