I never have just one project going - this could be why it takes a looong time to finish certain things. But I like to knit depending on my mood. If I want to be productive, I work on something almost finished, if I just feel like mindless stuff, I work on a blanket, if I want something done, I work on something small - or that needs to be finished by a certain time. And I put down unseasonal things too - I like to think my UFO's and the needles attached are resting
If you're bored, put it down - I don't know about you, but knitting time is too precious to me to work on something I'm not enjoying. If the yarn and pattern are good, you'll come back to it.