the knit list

What is the ideal number of knitting to have on the go at any one time? I'm sure that it differs for each individual knitter but I have discovered from experience that to have too many things on the go at once is too chaotic for me. So I'm thinking about restricting myself to the following categories:

1. sock knitting - always good to have a pair of socks on the go, currently Baudelaire
2. practical knitting - these are the things that are actually immediately required in the household, like mittens for baby bear and some wrist warmers for Tim; plans are for target wave mittens in recycled Opal sock yarn and Dashing in Jo Sharp Silk Road Aran Tweed (Highlander)
3. project knitting - something that I want to knit but that is not immediately needed; something to knit for fun; something to knit for the joy and challenge of knitting it; something like a Swallowtail Shawl perhaps?