Experts tell us that multitasking reduces our productivity. For some of us, that just sounds like common sense, but for others, we know it's just silly.
Knitters know that when their project is going slowly, one of the best ways to speed things up (barring an all-day TV marathon ), is to start another project. We don't really know why. Maybe the project you were working on was boring, and you just needed some space from it? Maybe you made a mistake and needed a confidence booster before going back and fixing it. Maybe knitting cables on size 1 DPNS isn't something you should do exclusively for two months straight. Whatever the reason, we can feel confidant that rather than detracting from our progress, starting something new can improve it.
When you hit a dead end, it's OK to back track and go around the problem. Forward motion is always better than standing still doing nothing.