I don't know about you, but I find if I have a project lying around that I know I need to finish, it messes up all my other knitting plans and I just end up doing nothing.
My second attempt at the Diagonal Rib sock has been about an inch shy of the toe for far too long. Every time I thought about knitting something else, my mind would slip guiltily back to the unfinished sock and I couldn't bring myself to pick up my needles.
After days of non-knitting I finally realised I just needed to finish the sock, so I did. Now I'm sticking with that feeling and getting straight on with sock number two of the pair.