I was doing the same thing - it was driving me crazy! I finally made a list - and so far I am sticking to it! Not sure how long I can be so strict on myself.
I am in the process of piecing a Friendship Braid quilt that my DD wants for her 1st anniversay this summer - the FB is boring to piece so I 'force' myself to do 1 panel between each project. I should be able to finish it if I stick with this method. LOL
Sometimes I can't sleep at night with all the ideas of quilts and color combinations I want to do........ I wish I could make them as fast as I can dream them up.