I will designate certain blocks of sewing for each project. If I know I am only going to have a shorter stint (two young kids at home means sewing time is scarce and often interrupted) then I may work on a project that is more easily interrupted. If I have longer stretches of time (and hubby has eyes on the wee ones) I bust out my never-ending FMQ project or any other project that requires work without interruption or will be more labor-intensive. LOL! If you are retired, I am guessing you get to determine your sewing hours without much interference, so perhaps just designating a block of time for each project? Or even a specific day - say Monday you work on rag quilts, Tuesday something else, etc.
I am sure you will get lots of good suggestions here - good luck!